Without doubting the wisdom of MB DOC...has your car been checked for the dreaded W124 cracked wiring harness problem? The V8's suffered from it just as the 6's. I've experienced such a problem causing a wide range of screwy behaviors in a 500E. Talk to your local dealer on replacement. MB may or may not replace on goodwill. I was fortunate that my local dealer did 100% on goodwill on a car that had 125K miles. They don't have an obligation past the normal warranty, but check with your dealer for possible goodwill. Its a common enough problem that an experienced tech should be at least somewhat familiar with it.
Hope this helps...Lee