Originally Posted by EricSilver

Several years ago, I had the exact same problem on a 260E, with the same engine. The culprit:

"Crankshaft Position Sender Unit" -- or Crank Sensor, in plain English.

It is a cable that runs from the back of the engine to the EZL(??) on the left fender. The insulation on the engine connection eroded away, exposing bare wires, which would short out when the engine got hot, but behave normally once it cooled.

About a $150 repair, parts + Labor.