I just purchased this '99 Jeep Grand Cherokee and didn't hear or feel this problem when test driving, and I don't know if it is normal or indicating a future problem. I am not very mechanical.
After I've gone over 15mph and come to a complete stop I can hear a "clunk" and feel the car **** slightly, but only a few seconds after I have remained at a complete stop. It sounds and feels like the transmission or 4X4 is engaging or disengaging.
The Jeep is auto transmission with "Quadra Drive", which I understand to be 4X4 that is on all the time, but only engages when one tire spins faster than the others.