I experienced the same situation early last summer. My MB also has a 103 motor.

Turned out to be the infamous OVP.

I removed it and while holding the flap shut, shook it. I heard rattling, indicative of an worn out unit. Replaced it and problem has not reoccurred.

I also lost a fuel pump relay(a few months earlier). When this happened, car would not restart until I jumpered pins 1 & 2 in the MAS unit. Your car may or may not have a MAS. I hope it doesn't -> $500.00 @ dealer.

What you've described sounds more like an OVP issue to me.

My 2 cents.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"