I have a C220 and I had this exact same problem a couple years ago. I also had a damaged engine mount at the time. The car turned into limp mode on me about 5 times over 2 weeks on the freeway and a simple turn off and on corrected the problem....pulling over without any power wuz the scary thing to do cuz ur car starts to slow down in the fast lane....

anyways, i suspected the car needed a tune up...
The shop i took it to replaced the Engine Mounts and did a complete tune up of the car, however during the tune up they noticed that my car's engine wire-harness had fallen apart aswell...so they changed that aswell.

It cost me a few thousand dollars to get everything done that time, mainly due to the price and labour for the harness job. However the problem never re-occured, so I'm guessing u need to look into those 3 things as well.

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Mercedes CLS
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