Answer:
Check for a loose ground
I had the same exact problem with my 95 C280. The instrument cluster circuit board is prone to cracking, resulting in an intermittent instrument problem. It had to replaced as a complete assembly ($1,000 P&L). That was a number of years ago and it has been fine since. I now have almost 300,000 miles on it with no other complaints than the head gasket oil leak. Cheaper to keep adding oil !