I've posted in the US forum as well of my problem, maybe someone here may have some helpful info.
At 22,000 miles I got an engine code & stutter...that turned out to identify a #3 cylinder misfire. It was erratic for awhile meaning after the engine was shut off then restarted the stutter was gone. I would reset the codes and be fine for awhile....Now the stutter is back with a vengeance. I have swapped the coil packs with no change, the plugs are fine. I asked a local vintage Mercedes repair shop for some pointers and he initially suggested the fuel distributor until I told him the stutter would go away after a "reboot"....
Anyone here have similar issues and know of a solution...At this point I can no longer drive the car...

 

Sounds like if it's not sparks - it must be fuel. The code should reveal more info than just "3 missfire" but to bottom it out you may have to take to a Merc dealership and conect it to their diagnostics with the engine running. Meanwhile, I would take the engine off, start it up in the dark and look around for any sparks jumping around from chaffed or damaged wires.