"EL. POWER CONTROL" Malfunction Message
 

I have a 2001 S320cdi which has an annoying, and potentially dangerous, intermitent fault.

It doesn't seem to matter how I am driving; just cruising, accelerating hard or whatever, but every now and then the engine will just cut out and the warning "EL. POWER CONTROL - VISIT WORKSHOP" shows on the dashboard. This is quite dangerous when I am overtaking on a motorway for example.

I coast to a stop. Put it in 'park' and it re-starts no problem at all. The problem will sometimes re-occur a mile or so down the road and sometimes does not re-occur for weeks!

Has anyone got any idea as to what could be causing it?