I remembered same thing happened to my W210. Try changing the battery. For me, it is the weak battery that causes havoc to the system. The meters swing eratically upon starting and engine sputters, I was always scared of the engine stalling at traffic lights. After The battery change, every thing went back to normal.
However, I did change my wiring harness, but after 3 months later. As I discovered that the insulating sheaths are broken and chances of washing the engine is going to blow up the electronics.
The other day, my exterior side mirror did not work and fuse kept blowing. I opened it up and found all the 6 wires bare. No sighs of the PVC sheathing. If I were you, I keep a look out.
Hope this helps