Motor is hard to start after warm up

Well I drove the car to church this morning and it cranked fine as it always does when it is cold. After chruch (1hr 1/2 later) I got one of my buds to come out and give his thought on it. I told him the deal and I just got in didn't do anything but turn the switch and it fired up after about 4 seconds of turning over. He really didn't say much but it seemed fine to him. But now after driving it some more and taking note of how long the cars sits after warm up it only acts funny when it sits between 15 min to 30 mins. It seems that if it sits longer that a hour it will fire up better. I might need to add that when I come home and shut her down I can just tap the switch and it will fire up on the spot. I looked at the carb yesterday and in between the carb and intake there is a gasket, metal gasket and then another gasket. Like that is maybe some kind of heat shield. ???