MBWorld.org Forums - RPM's fluctuate up and down while at set speed? Please Help

Hello everyone. Im a new proud owner of a 1996 S500 as of this week. The car is border line flawless cosmetically speaking. The car however hasn't been driven much in the last couple years. The guy I bought the car from is a mechanic and seemed to have taken great care of the car. It's got 103,000 miles on it and he said he had the tranny checked out by someone who specializes in mercedes and they said everything checked out just fine. I have however been noticing lately that while I'm driving about 40mph or so the rpm fluctuate up and down a few hundred rpm. It's very slight but none the less present. It only does it on occasion. I'm notsure if that's tranny related or what. Also some times while letting off the gas to slow down, theres a slight jerk, almost like the tranny is downshifting but not smoothly. Im not sure if this is normal or what because it doesn't do this all of the time. Any help would be greatly appreciated.