Check your entire engine wiring harness closely. I had to replace mine several years ago because I was having more strange problems. I noticed that numerous wires had cracks in the insulation with some exposed wires. Arcing was occurring in some places. The insulation was brittle and flaking off in many areas. From what I could find, Mercedes was using biodegradable wiring harnesses during that era. My car has mostly been out of the weather and garaged it's entire life, so there is no other reason to expect normal wiring to do this. The car has been perfect since replacing the harness.

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1996 E300D