Vibrations that you describe are sometimes caused by flat spots in a tire from sitting in one spot for an extended time. My '02 C320 does this for about 5 miles in the cool N.E. mornings (<50 degrees)
First, the Continental tires (Conti Sport Contact) are junk. Noisy and lousy grip for Summer tires. Second, I think the MB suspension amplifies this more than the American car suspensions. I know a couple of folks with MB's and they complain about the same thing.
Also, try rotating the tires and/or rebalancing.