My SRS light was due to a faulty "horn contact ring". It sits on the undeside of the steering wheel. No outward appearance of failure but I was relatively certain that this was the problem. My intermittent SRS light sometimes coincided with the turning of the steering wheel. I first replaced the much cheaper brushes to no effect. You might check all your seat belt connections first.

glenmore
1991 300CE
2000 C280
1990 LS400