Sticky Pedal

i'm not sure if anyone else has had this problem but on really hot days my gas pedal gets kinda stickey, what i mean is that it gets harder to push and moves back slower, up untill a few days ago it was just kinda annoying but latley it has been sticking down part way and i have to reach behind it with my toe and pull it back into place in order to slow down. if anyone had had this problem or has any sugestions... thanks in advance