I have a 2009 Subaru Legacy…For the last month it has randomly not started …usually after doing several home visits with client !,!not handy 
I got a new battery, my alternator and starter check out OK …according to 2 shops, one a dealer. The dealer says they can,t fix something that isn’t broken …checked all things elecronic, all checks out OK.
I have noticed when it happens, the hood feels hot…after sitting for 30-45 min.while I am doing a visit. Usually it would start when my husband comes out and jump starts it. But not this last time …had it towed to the dealer …they could find nothing…he says “it starts right up”. So I am picking it up from the dealer , but it is not fixed, and will happen again. The head mechanic seems mystified. …or tired of me calling. ANY IDEAS?
Try an independent owner-operated shop.
It sounds like you may have a component becoming sensitive to heat. The dealer either isn’t motivated or isn’t interested.
What, exactly, happens when you turn the key?
If it doesn’t make any noise when you turn the key, try moving the shifter from park to neutral and try again. It could be the park/neutral safety switch.
The next time the engine won’t turn over, with the ignition switch on, step on the brake pedal and shift the transmission into neutral and then try starting the engine.
If the engine starts, the problem is with the park/neutral safety switch.
https://www.rockauto.com/en/moreinfo.php?pk=3970494&cc=1443525&jsn=349
This is a safety device that prevents the starter from operating if the transmission is in any gear.
And because they’re made of plastic, heat can effect their operation.
Tester
Good ideas above. If it isn’t any of those, suspect a faulty starter motor. Starter motors can be heat-failure items, especially if it is located close to the exhaust system, which isn’t that uncommon of a thing. . It sounds like you’ve done the right things up 'til now, and the shop is telling you it doesn’t fail when they test it, so they can’t fix it. Another version of what they are saying is that while it might be the starter motor, they can’t verify that’s the problem, so are unwilling to risk replacing the starter motor for fear you will accuse them of cheating them and demanding a refund if it doesn’t fix the symptom. They don’t want to take on that risk of customer dissatisfaction and bad-will.
So one option, tell them if they think it might work, to replace the starter motor and you’ll accept the risk yourself if it doesn’t fix the problem. Worse case, you’ll have a car that still won’t start on occasion, but at least you’ll have a new starter motor.
If I had this problem, what would I do? hmmm … No crank when hot, eh? … I guess when it wouldn’t start I’d get out a stick, like a broomstick, and whack the starter motor. Sometimes doing that will disturb it enough to then crank. If hitting it with a stick worked – you’d know for sure the starter motor was faulty.
Mechanics can also test the voltages at the starter motor during attempted cranking, that test often gets to the bottom of this problem too, even if the car cranks ok and starts at the time. But there’s some chance the result could be ambiguous, especially if you have a heat-related problematic starter motor, in which case the test would be a waste of money and you’d be better off just replacing it.
Thanks so much for the ideas … will try the moving to neutral idea … and if all else fails, a new starter.
Nothing happens when I turn the key … no noise at all. Everything works when this happens: lights, windows , radio. And it is random … about 1-2 times a week. Will post the outcome.
I think you’re headed down the right road. Sounds like the starter solenoid is going. That’s a thing that both engages the starter motor’s gear to the flywheel and enables the starter motor circuits. Generally the solenoid is a part of the starter assembly. Solenoids can and sometimes do become heat sensitive with time and exposure.
Solenoids usually make a single click when they go out. I’m betting on the park/neutral switch.
Actually, when the solenoid goes out it’s silent. It’s when the contacts in the Bendix assembly get fried that the click of the mechanism is heard without being followed by enabling of the starter motor windings… click followed by the silence of no starter motor running. A solenoid that does nothing makes no sound.
That still, however, doesn’t rule out the park/neutral switch as a possibility.
Battery connections are the first place to begin when you have a “No Crank” situation. Even
if you have a new battery, if the connections are loose, dirty or corroded, you will not be
allowing the full flow of current to pass thru the connections. The connection may be
enough to turn on the lights, but not enough for the huge flow that is needed to operate the
starter. This is where many people say that they know the battery is good….”because the
lights come on”. This is no more a battery test than licking a 9volt battery. It only tells you that there is electricity…not how many volts or the amperage that flows from the battery.
Jump starting may have wiggled the terminal just enough to allow the current to pass and start the engine, but tomorrow you have the same problem.
First remove the cables from the battery and use a wire brush to remove any corrosion and dirt from the battery posts and the cable terminals. There is a tool with a round wire brush for this purpose, found at any auto parts store for less than $10 http://shop.advanceautoparts.com/p/kd-tools-terminal-battery-brush-kdt201/25980576-P?searchTerm=terminal+brush.
Before connecting the cables, apply a coating of di-electric grease to the battery posts this will keep oxygen away from the connection so that it will not corrode as fast.
It is just as important that the other end of the cables also have a clean connection. Remove the positive cable from the battery again so that you do not short anything out. Follow both cables to their far ends, remove this connection and wire brush the connection and the cable terminal clean and retighten these connections.
If there was work done recently, there may have been an “engine to body” ground that was not installed following the work. These grounds normally run from the rear of the engine to the firewall and are uninsulated and most are a braided wire. If any of these are found unattached…reattach them.
Remember….this is not a “Sherman Tank” don’t over tighten the connections.
Tight…tight………………too tight…broke!!!
Yosemite
More good ideas … will clean the connections and check for wires. Found out I can’t move the gear shift into neutral if the car isn’t running (you all probably knew that) but my son-in-law showed me a “re-set or release” button … hidden just above the PARK position … have to pry off the little cover and use a screwdriver or the key to hold it down inside … as you move it to neutral. They know this because their Subaru has a park/neutral switch problem too … but can’t always get it to shift out of park … learning more every day …
Actually, when the solenoid goes out it’s silent. It’s when the contacts in the Bendix assembly get fried that the click of the mechanism is heard without being followed by enabling of the starter motor windings… click followed by the silence of no starter motor running. A solenoid that does nothing makes no sound.
There are no contacts in a starter Bendix, it’s a mechanical drive with an overrunning clutch. The contacts you mention are in the starter solenoid.
The contacts are in the solenoid ASSEMBLY, not the solenoid itself. The mechanical drive that engages the starter gear is activated by the solenoid… the starter gear is slid into engagement by the solenoid. The contacts in the assembly are also engaged by the solenoid. If the contacts are fried, you’ll hear the click of the starter gear being engaged followed by nothing, since the starter motor windings will not energize. If the solenoid itself is bad, NOTHING happens. No click, no motor, nothing.
The “Bendix assembly” is the term commonly used to describe the assembly that the solenoid moves that engages the starter motor gear to the flywheel ring gear and closes the contacts that enable the starter motor circuit. It should be noted that modern designs often vary from the actual original Bendix design that made cranks obsolete, but the term is used generically, much like kleenex or windex.
To KEITH and TESTER 
you were right!,! The park/neutral safety switch!! When it happened again today …I just jiggled the steering wheel and it started …the 2nd time I pried open the bypass switch pressed it down with my key, switched to neutral and it started right up!! YAY!,thanks so much!
Congratulations and sincere thanks for posting back. It’s always good to hear a happy ending.