Take the car to an independent mechanic, there is something wrong with the transmission or ring gear if it makes noises like that. Could be a bad starter or bad ring gear, or both.

Benz starters have overrunning clutches, so if the solenoid is stuck the engine won't drag the starter motor, but that clutch will make terrible noises if the starter gear is touching the ring gear while the engine is running.

This car is sorta young for this kind of trouble, though.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!