w140 ASR woes (sorry!)

[plink49]

Today for the very first time I experienced the dreaded ASR light and going into limp-home mode where the car becomes, literally, a powerless slug. I eventually realized after actually limping home 7 miles at 15 mph, that all it took was a restart of the engine and everything was fine. I went back out and drove around close to home to check it out and all was well for about 5-6 miles and it did it again after accelerating from a stop (the first time was decelerating TO a stop). I can't possibly see any connection, but I changed the oil and filter immediately before this occured today.

Okay, I have read through all of the posts (well, most) regarding ASR, limp-home problems from a search, and what I got out of them was that there is nothing definitive that causes it, and in fact could be one of 15 or 20, some being extremely expensive. My questions are these:
If I understand correctly, ASR is an anti-slip (traction) mechanism. Why then do things like brake light switches, neutral safety switches and throttle switches have any bearing on it? and why does the car lose 90% of it's power? and what connection does the tire chain switch have to it (is it a type of override)? Secondly, what is the first logical step to take? Thirdly, is the computer diagnosing strictly a MB dealer function? If so, from what I'm reading, that is not all that reliable anyway.

Help from anyone is appreciated, but particularly someone with a '92 500SEL