My car did that one time. It was about 6 months ago. I was at a mall, started it and the whole car shuddered the whole drive home. Was not as bad on the freeway. Once I stopped the engine and re-started it again, the problem has never recurred. The idle seemed fine too.
I thought it was the motor mount, but it never happened again! Maybe it's something with the M104 engine?!
2006 E350 w/ 155k miles (Daily Driver)
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)