Why when I put gas in my car it has a hard time restarting?

What is your question?

When I get to the gas station I turn my car off and put the gas in the car once I'm done I would tighten the gas cap get back on my car and try to restart. It cranks for a while before it would starts, sometimes I would have to push the gas paddle to get it going, but knowing that I have this issue I would try to leave it running and put gas in but it would shut off sometimes or sound real ruff. I had it checked at auto zone and it came up with a gas cap code but I'm now thinking that it might be something different. Please tell me what could the problem. Thank you Kelli.