Pull the wheels and check to see if any are grounding out.
It could be an inner pad is worn.
IT could be the way the sensor wires are routed, or it could just be loose.
The sensor has to make a ground contact to light up the gauge cluster light.
You might have rear sensors, some cars do. Check those to if you got em.
If you need pads, order em for partsshop/fastlane on this site.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.