My Dad's C230 (M111 engine) did the same thing. Swapped the plugs, as they had been in there since new, and it solved the problem right away.
Your M112 engine has twelve plugs rated for 160,000 kilometers, but they don't really last that long. Have they been replced lately?
Joe's comments about M112 MAS's are a good place to look too. Lots of M112 equipped cars need new ones.
Is the car lighting the CE warning lamp? If so, codes will quickly tell you what's going on...
1998 C230 "Black Betty"