So I have a 2003 focus. It runs well except that every time when I drive it for a bit long, like for 30 minutes, and I turn off the engine, and then when I try to try it back on, it just won't start. But when I cool it down for like an hour, I can turn it on again.

I had it checked a couple of times but no problem found, it is not the problem with the starting system. Could any one here tell me what the problem is?? THANK YOU!!