I have a nissan maxima 04 and when I switch the gears from park to drive before I can even push on the gas some times the whole car jerks then rides smooth till the next time I switch back into drive it might jerks again makin one big thump sound. wat could be my problem here n how can I fix it any 1???

Ill assume only occurrs when drive train is warmed up...cold ok?shift valves sticking in valve body and a very common problem with these vehicles equipped with 5 speed auto trans.check fluid color.brown is normal on these units....black is bad.if its still brown and not black replace the valve body to eliminate this concern.its alittle pricey but about a third of the cost of transaxle replacement.