Hotee18m, Don't jump to conclusions. In my case, my C280
began to have bumpy idle after I got it back from my
30K service (archive threads can explain).
Anyway the aftermath explaination was that the 'camshaft
adjuster magnet' had to be replaced. Although the rough idle stopped, I often wonder if it may have been
something like bad gapping on new plugs, wrong type of plugs or something that the mechanic did not want to 'fess up to. Since I didn't pay for all the extra stuff, I was satisfied
with the end result. So, indeed this magnet may be a component to idle smoothness, but in your case it may be a simple need for new plugs.
Check your wiring harness anyway. Other posts point to 60K miles+ as the magic number for harness deterioration signs.
1979 300D 199 K miles
1995 C280 95 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles
1979 240D 140Kmiles (bought for parents)
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD