Just got back late last night, haven't had a chance to check anything out yet though.
Yes, the 560 has the "B" switch for 1st gear lock, but I have only locked it a couple times. The most recent manual 1st gear lock was probably a couple weeks ago. Will keep that in mind if it happens again.
Don't think it could be the kickdown switch because of the circumstances when the event happened. I was rolling at speed, slowed to a stop. Light went green and I gently accelerated and made a right turn. That gentle accel caused a 1st gear start.
Will also have to check out if I may have had a minor coffee spill right into the "B" switch. Possible a liquid short could have caused this.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.