I had a customers car do this on me before, it was a '73 450SE to be exact. Turned out to be the trigger points for the EFI system.

Unplug the wire harness on the top of the motor up front, try to start the car and see if it acts the same way, if so i personally think its the trigger points.

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg