Just a comment (I am still getting to know my 300E)
6 yrs ago, my instrument panel was acting crazy - gauges moving wildly (sometimes working correctly), it started to become more of an issue, and if I recall correctly maybe a low battery, it turned out to be a voltage regulator/brushes. You may want to check it (just to get it out of the way) part is about $30 (others suggest to keep the old part as backup).
see this other post
http://www.peachparts.com/shopforum/showthread.php?t=104471
I have also noticed a random ABS light on / off for the past two years or so (topic for a separate thread) - may be related to the OVP Relay (which may also be a solution).