vapor lock

the car starts cold fine. but after driving for a while and parking at a grocery store for instance, it will start and run for about 30 seconds and then die. i have to wait 45 to 60 minutes for it to cool down before it will start again. this usually happens on warm days, hi 70's and up, but it is happening with cool temps also. this has been an ongoing problem for a year now. my mechanic keeps replacing various parts, but the problem continues. your thoughts?

thank you

alan hatley