I know your current draw could be from a number of things but.....I had this problem (92 300E) and after checking with an AMP meter in my case, when I unpluged the cable that runs from the radio amp unit (right side fender well) wire that runs down to the becker CD changer. Follow the wire you will find a 4 wire connector to unplug and see if you have the same problem I did. Mine too was intermitent and would drain the battery completely.

Good luck buddy,
Acky