Just FYI.
The original alternator on my 1988 300CE failed on me a few months ago. I have 135,000 miles on the odo. Nothing lasts forever. Not an expensive repair. Get it checked out before you get stuck on the road at night.
The night mine failed, the first bulb to light was the SRS. About a mile later another came on, then the radio died & I knew it was gonna be a AAA ride home.