Engine shuts off and won't run or start if turned off?

Runs perfectly but once it gets hot will either die out and not restart or will run fine until I turn it off to run into a store for 30 mins but won't restart until a few hours later. The engine turns over, and sometimes catches for a second or two but makes awfull sounds and dies out. I let it cool for a few hours and it runs perfectly for another 10-20 mins. This is an ongoing problem that has been getting worse and worse. I replaced the fuel filter, crankcase filter, air filter, spark plugs, spark plug wires (as I noticed the spark was weak in a couple of the wires) and it ran better but still has the problem after driving for 10-20 mins. So I decided to replace the cap and rotor, as I was doing so the metal on the sides of the distributor broke off in my hands. So I replaced the Distributor and the truck seemed to run well, no more backfire, no more hesitation I thought I had it fixed. Drove it around for 20-30 mins no problems. Parked at the mall came back 45 mins later and it would start for 1or 2 secs and die rough. After trying like 10 times it started and didn't die out. It ran rough for about 30 seconds while I let it warm up but then once it settle down it was fine the entire drive of about 15 mins to my next stop. I Parked it for 5 mins while I picked something up and came back and the problem got worse. It would start but die out within a second or 2 after making ugly sounds. I kept trying to look for the problem under the hood while my g/f tried to start it but no luck, then eventually it started and ran. Drove home 2 mins away no problems. Once I was home I parked turned it off and it kept starting up perfect over and over again. What is wrong with my truck, please help! The same thing will happen tmrw but only at the most inconvenient time.