When was your last tuneup? Might just need wires and plugs. Get the codes read - maybe it is a simple P0300 type misfire code...

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280