My 1991 Sunbird is giving me fits. I can sart it up easily when its cold but it is after a 25 to 30 minute run that it wont it will crank over but no spark what so ever, but then you wait for a bit say 10 to 15 minutes and it starts right up, never dies just dont shut it off

which is kinda of like lottery starting which really sucks because I have very few positive hits, more negative not starting after a 25-30 minute run. I have changed the coil packs and it still does it. It is a 4 banger 2.0. I have read some other posts that have had simuliar problems. So I started doing some research. Could it be the crankshaft sensor or the camshaft sensor? The answer is no. because according the Mitchells and the dealership that year does not have either one. So I am kind of at a stand still on what the problem is maybe someone here can give me some better insight one where else to start. Thanks