1999 Chevy Suburban Shifts hard

I have a 99 Chevy Suburban, and everytime I drive to the other side of town on the freeway the truck works great, but once I get off the freeway it starts acting up. If I pull to a stop and then try to go again the truck shifts really hard, sort of like it's kicking to go forward. If I stop and turn off the engine for five mintues then start it and get going again it works fine again. I'm not sure what it is. We recently change the thermostate, fuel pump and filter, and got a new battery.