I'll defer final judgement to Benzmac on this one but I've observed the same symptoms in a 95 E420 on occasion. Don't sweat (no pun intended)the A/C making the car feel dead, it is a real power-hog. When I've observed the sub 500rpm idle (would guesstimate 350-400rpm) you can occasionally feel a tiny (read: a non-MB owner would probably not feel it) bit of shake as well. Never does it very long, just 10 or so secs here or there. Mostly only seen at stoplights or braking up to a stop. Since it isn't readily repeatable I have not run it by the Benzmac. How often does your car do this? Is it repeatable enough to show your tech on a test drive?