Brake warning light mystery
 

I am looking for likely suspects for a brake warning light that lights up very inconsistently and without the brakes being used. The pads look fine and the fluid level is also good. Any ideas on what else could be causing the light to go on occasionally? When it goes on it is not a consistent blink or steady illumination. It just occasionally lights up and correlates with nothing that I am aware of. It is a 1995 E320 wagon.

Thanks very much,
Jim Lee