I've had similar problems and, in 35 years' MB ownership, I have never changed an ignition coil.

If you feel the distributor cap, rotor and HT leads are ready for a change, do ensure you get the best quality parts. My advice is to go to MB dealer and ask for discount.

I have had trouble with after-market ignition components and have regretted not getting the good stuff from the outset. Having said all that, I got Beru HT leads 2 years ago and they seem fine. Similarly Beru plugs seem excellent.

Good luck to you.

RayH