C320 vibration while stopped

I own a used 2004 Mercedes C320 4Matic. I bought it with 57k miles. I drive it about 150 miles per week. The reseller told me i needed engine mount replacements at 67k. The car did have a vibration, which I was sort of ignoring, so I had the work done. Now, the vibration persists. It is most noticable in the morning upon start-up, at an idle. But it is also noticable when the car is warm and I am stopped at a light. It can also be noticed as a subtle vibration in the steering wheel at highway speed. I am very sure it is not wheel balance or rotors (hey, I can feel it at a stop).

I brought it back to the dealer, who said after 5 hours of diagnosis, they could findind nothing wrong.

Anyone else experience this?

Steering wheel vibration is probably not related to the engine vibration. Steering wheel issue could be unbalanced tire, switch tires front to back and see if this changes anything.

Are you using the correct octane gasoline? How do the spark plugs look?

Vibration when stopped…not tires.