As per the title I have a 2000 C280 (M112) that has a significant vibration at idle. It can be felt at the engine in neutral and really felt in gear. Mileage is 212.000. There are no codes. The car runs fine above idle and gets excellent fuel economy. The following items have been done in the recent past:

1) Motor and transmission mounts (dealer sourced) 4 1/2 years/70,000 miles ago.
2) Spark plugs (dealer sourced) 3 years/35,000 miles ago.
3) MAF cleaned recently.

I have tried the "torque test" for the motor mounts (put in drive, step on gas - same in reverse) and the mounts seem good. There is no sign of leakage of the fluid from the mounts.

Ideas? I would think if I have a coil or wire problem I would get a code, but as I said, there are none.