throttle body and sensor might be needing some cleaning, make sure that you are only using premium unleaded, add a can of chevron techron injection cleaner, fuel filter change, air filter change.
I had a similar problem once in my 560 SL, it "coughs" once in a while. Semi-rough idling, so I did all of the above and it apparently fixed the problem. What I would have done differently though is do it one at a time and see which one would actually fix the symptom, so it can be a learning experience for you as well.
1978 280 CE silver
1986 560 SL black
1987 300 SDL cream
1994 SL 500 brilliant green
1997 E 300d dessert silver
2005 FORD F250 Superduty Crew cab 4x4