Car jerks when shifting to R

[zuvarak]

As the title suggests, for quite some time my e53 has been doing this weird motion when selecting R. It doesn't seem like the standard transmission jerk that I've read about. Once R is engaged, I can literally feel the car creep a little backward, meaning that the wheels are literally rotating slightly. Does the same when going R > D, but not as much. Someone told me that it's probably a worn-out transfer case. Any ideas? If it's the transfer case, then what exactly could be causing this behavior?