Why does my car shake at idle or slowly in reverse? on 2001 Mercedes-Benz C320

The mechanic did not know, other than motor mounts?

Asked by for the 2001 Mercedes-Benz C320
Put a floor jack under the engine and jack the engine slightly. If the vibration or shake goes away then it is probably motor mounts. Greg's Orange Auto is in Orange, take it by he will check it for you.
Thank you so much! I'll do that for sure. I really appreciate it.