Does it feel like the transmission isn't catching the reverse gear?
I have this problem too... sometimes when I push the gas, it feels as though it's barely in reverse (if that makes any sense), and then when I push on the gas (some more), it will catch and jolt the car. Does it feel like your problem is trans related?

I got an answer to this a little while back. Don't recall what it was though... I'm sorry,,,, Do a search! You'll find the info. Also, it doesn't seem to be any sort of major problem.

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
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!)