Strange Problem, turn key, car starts, runs fine, no electrical?
Any light on this situation would help, something with the fuse box? corrosion somewhere I should check?
The car has a new battery so I know its not that.
Reading the forum came up with possible the EIS or the front SAM. Just wondering if there are some connections or wires I should check for corrosion, sounds like an electrical connection somewhere is corroding and getting worse.
Front SAM is located under the hood right corner. Check out the pic below and try to see if anything is loose and such.

It would also help if you can find someone with STAR (Mercedes Diagnostics Software) to do a scan to really for sure find out.
Good luck,
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