It could be low voltage from the alternator, a bad capacitor in the instrument cluster (voltge regulator), maybe the relay. Mine started doing it out of the blue, wipers, turn signal, the SRS comes on. Then they all come on and the guages go to zero for a second. It has not done it lately. Do a search on, http://www.benzworld.org/
there were many postings including pictures
http://www.benzworld.org/forums/search.php?searchid=944083