2010 Volkswagen CC luxury

I just bought a 2010 volkswagon CC with 125k miles and when I test drive it everything was great and working perfectly. After driving it for a while every time I came to a complete stop there was a hard thump as if someone slammed the trunk. This only happens when the car is warmed up. After it thumps hard and I go to accelerate it stutters and wants to go and all the rest of the gears go through great until I come to a stop. Also happens sometimes going from R to D.