Same thing just started happening on my 98 M3 conv. Same symptoms, cuts off and on, lights on control panel will sometimes stay lit, seems to happen more in the hot summer afternoon, sometimes all leds, lights will go dead. Starts up mext morning everything fine for a few mnutes then ti 'll happen again.
Awesome posts so I will try this asap.
REMOVING OLD SOLDIER- I used to do very light soldering on pc boards. There is some Solder remover that will suck up the old solder in a second. It's awesome. It looks like some braided mesh copper about the width of a shoelace. Very cheap to buy at radio shack, etc. Just put the copper mesh over the solder and apply solder iron heat and this stuff sucks up the melted solder like a sponge.
Think I might take my car over to a BMW mechanic and just test their honesty/knowledge. Anyone willing to bet my part will "need to be replaced" with several hours of labor?