Mercedes mystery

I have a 2000 Mercedes E320. Starts fine every morning, but every once in a while it randomly will not start back up again if I drive it a couple of blocks and shut it off (this happens on my lunch hour). When I try to restart it, it will sound like it is going to turn over, but it just doesn’t get there and I’m afraid I’ll flood it. But, if I let it sit for about 30 minutes without trying to start it, it will start right up and run fine. Again, it is very random and can go for weeks or more than a month without doing it. And, it only does it after I drive it very short distances and then turn it off (less than 2 or 3 miles). I’ve taken it to a mechanic, but, of course, it’s always running fine when I do, so he’s not sure what it is. I’ve read online that perhaps it’s a sensor of some kind?

Its possible that its flooded already. The next time it happens, floor the gas pedal while you turn the key and see if that helps. (This is a flood clearing procedure). If that helps your mechanic might be able to figure out if something like your fuel pressure regulator or a fuel injector or two are leaking gas into the intake.

At this point it would likely be a small leak and these events may be related to just how cold the engine is when you run it only briefly. When an engine is cold it runs rich (more fuel than normal) until it warms up. If you’re shutting down with a a rich mixture with a bit of a leak from regulator or injector you’d end up flooded.

A good mechanic might be able to tell if something like this is going on by the smell/condition of your oil.