Heater Blower, on & off, 300E, 2.6, 1992
 

Please advise where to begin trouble-shooting. Had heard some "squeaking" from under the dashboard last week. Then, this week, all of a suddent, the blower motor for the automatic climate control did not come on. After about one hour into the trip, it did come on, set at high. The next day it did not come back on.

It sounds like the blower is dying. I'd unplug it before it frys the CCU or the Relays that support the blower or CCU. Don't know where the blower is on your car, but on the 126's it's under and behind the passenger side bolester, under the glove box. I just replaced my blower with a new after market one I got online.