I had a similar problem on a 1989 260E...Here's what it was (after over a year of screwing around)...the electrical connector for the twin fuel pumps...under the rear seat near the vacuum motor....

It was green with corrosion...I thought I could clean it up but instead I removed it and soldered the wires together....

The stalling and dying never happened again....but by the time I got all of the "quirks" solved, some dumbhead ran into the rear and totalled the car....my daughter got out without a scratch...

That's life,
The Tenor Man