1993 300SD W140.

Occasionally while driving and I move the Turn Signal Arm to indicate a lane change some of the Instrument Cluster Warning light flash once really fast and then the RED Fasten Seatbelt Light continues to flash for about 5-7 times afterwards.

(It’s hard to see exactly what Warning Lights flash because it happens so fast, but you can see various Amber and Red lights flash)

Sounds like a short somewhere??? Any ideas?
Wiring Harness has been changed about 4 years ago.

The only other electrical problems are non-functioning Drivers Door Speakers & non-functioning IR Keyless Remote.

Any help appreciated.