Won't start after the engine been running for 30 minutes. I have to let it cool down

What is your question?

I will be driving on the freeway for 30 minutes, the truck will be running great. The temperature gage needle is in the middle. I will pull in for fuel and it will be difficult to start. After the third attempt it will start but it won't run that great. The check engine light will go on but it will reset itself after a day or 2 of driving. Thinking that leaking injectors could be the cause of my problems, I added some fuel conditioner to correct the problem. That was a mistake. Once again I shut the engine off after running it for a while and when I tried to start it 10 minutes later it would barely run. It was running on only 10% of it's regular power. The engine temperature started to climb. I pulled into a gas station 5 minutes later and filled the tank with high test fuel and let the engine cool down. It's engine is performing the way it did before but I don't dare shut the engine off when it's warmed up and try to start it 10 minutes after. Could you tell me what is causing this condition?