My SRS light was from the horn hub. Easy DIY but an expensive part. One of these things:

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=22Z02QIPG22Z02QT5V&year=1991&make=MB&model=300-CE-002&category=M&part=Horn+Contact+Ring


Check the easy things first, seat belts, buckles. Sometimes the voltage regulator, loose ignition tumbler. See if you notice any relationship with the light flickering and turning the steering wheel.

glenmore
1991 300CE
2000 C280
1990 LS400