So I’ve had this problem for a week or so. The cold start is usually good and the car would usually just start but whenever I stop to go to the store for 5-30 minutes or so, I come back and the car would start only on 2nd try. On the first try the car turns over but won’t start. The second try usually starts the engine. No weird symptoms or noises just this. It runs fine and silent. I haven’t observed any power issues or anything like that. What would you check first ?
Hyundai Matrix? Where are you located?
What do you get if you turn the key to ON for a second, then OFF before you try cranking the engine?
I live in Norway. The car, Hyundai Matrix is also called Hyundai Lavita in Asia as far as I know. It’s weird that this site doesn’t recognize it. Probably because you don’t have one in USA but believe it isn’t anything to sigh about, it’s ugly as shit. I use it for work.
It’s no use trying to turn on the car now since the car has been sitting outside for a day and it would cold start alright as always. I’m just worried that soon it won’t start at all so I’m just wondering what this could be. Some lost pressure or ignition coils? When I turn the keys and it’s ON I get all kinds of lights on my panel as most of the cars do. I don’t really have any light that should turn off before I try to start it if you mean that. These warm starts were always successful with the first attempt and now they are not. I mean. I could let it be but once I tried to turn it on for a extra minute or so and I like to take care of things right away.
Our Matrix is made by Toyota. We have to be sure people know what car they have - you’d be surprised how many people don’t.
You should consider yourself lucky. Pininfarina designed your car. They’ve done the bodywork for some of the most legendary Ferraris in history! 
Your problem sounds a lot like a bad main fuel relay. When their solder joins go bad, they tend to lose contact as they heat up due to expansion. So they work just fine when things are cold, but after it’s warmed up, they start behaving oddly. That’d be where I’d look first, anyway.
Appreciate it. I’ll try this right away. Also. Would you suggest it might have anything to do with the ignition coils or not ? I don’t really know how they act when they are faulty so just asking. I read that they normally do the annoying things in cold starts and it is hard to start. Mine really isn’t hard to start. it just starts on 2nd try or so.
@shadowfax and @ga4a89, if you believe the car has a fuel problem, why don’t you just hook up a fuel pressure gauge?
If the car fails to start, look at the gauge and that’ll give you some, maybe not all, answers.
@db4690 'cause I’m not there, and I never assume anyone has tools unless they tell me they have them.
Based on your description of the problem (and my assumption right or wrong this car has an automatic transmission) it sounds like a faulty neutral safety switch. This usually manifests itself with warning lights on and stone silence as far as starter motor and starter solenoid operation.
Next time it acts up, shift into neutral and see if it starts.
@ok4450 the engine should not turn over if the neutral safety switch is bad. OP stated it does on the first try, but does not fire.
You’re right; I’m wrong. My train of thought led me off in another direction and I forgot the OP stated that the engine would turn over. My bad. 
Since this is Europe, it is more likely a manual transmission.
Solved It was the starter dying. I changed the starter and the car is working just fine.
All above good comments. Another idea to consider. There’s a possibility the mixture is too rich on warm starts. The ECM is supposed to adjust the mixture (using a combo of fuel pressure and injector timing) based on coolant temp. Leaner when warm. Checking the coolant temp sensor and fuel pressure regulator would confirm/disprove.
Verifying the vacuum hoses and components are not leaking is probably worthwhile too.
@ga4a89 thanks for the update!
And congratulations!
Can you please post a picture of your car? Over here, we don’t have a Hyundai Matrix.
The starter? That’s surprising. Usually when the starter is on the fritz, it first shows up on cold starts, not warm. But the critters are complicated these days. I think if you listed every known failure mode a car could possibly have, some car or another out there has had it!
Thanks for posting the finale @ga4a89! Its useful to know how it was resolved.