My 1988 f150 acts like its has a dead battery after it get hot and i try to start it. The truck starts up everytime cold and if i wait 20 minutes after driving it will start up. But if i try to re start the truck right after driving it turns over really slow. I have a new battery and starter relay i am thinking starter because i had this issue on a motorcycle before and it was the starter i just wanted opinions from others

 

Grounds being corroded or not making good contact could also cause this condition.

 

I'd go with starter if battery and cables are good. Possible Heat Soak condition; especially if starter is located near header, exhaust, etc. No idea if a heat shield for your particular application is available. I made one from a Dr. Pepper can for a big block Corvette which had a history of eating starters prior to. Regarding the cables, you need to go beyond checking only the connectors. It's not uncommon for corrosion to run through the cable within its sheath.