LevZeppelin

My truck runs fine except for one problem, if i get stuck in traffic and it sits idling for a while it gets flooded with gas. at least i think it's being flooded with gas. when i start to drive, it moves really slowly even if i floor it, and feels like it wants to stall, it occasionally does too . if i keep driving, it eventually clears out and runs fine. what is happening? my theory is that it is running rich and floods while idling(just a guess though). any advice? thanks.