2001 Ford F150 transmission problems?

[Gregory]

i was at a red light and when it turned green i started going and the truck would not pull very good,it would only get up to 20mph or so,then i start seeing smoke coming up through the cab and in my rearview mirror,so i pull over and i can smell the transmission fluid,the truck sets there for an hour or so and i start it up and drive off with no smoke or problems,couldn't find a leak anywhere