Does your car have ASR (traction control)? Can you describe what leads up to the power loss? Has the wiring harness been replaced? Both the traction control system and wiring harness can cause drivability issues and therefore may be suspect. I would start by retrieving codes from the computer. If I'm not mistaken, you can check for a fault code without the use of computer on this model. A quick search of this forum should reveal a ton of info as the above two problems are very well known on the W124.