As a follow up to this, I have finally found some time to experiment:

I have found that the ignition switch is not the culprit. I initially found the cables plugged into the ignition switch needed reseating as they had crept out a fraction.

Upon trying the ignition everything worked as it seemed it should ... so I put everything back in place and used it for a week or so.

A few days later I noticed that there was an odd sound beginning to reoccur after starting, almost as if 2 plates were just touching as they rotated.

This sometimes became more evident when moving from Park through reverse, neutral and into drive and then back to park.

In particular, it would happen if I engaged either Reverse moved the car a foot or so, then into drive to return back to the same spot. Conversely it would do the same when I first went to drive and then to reverse.

Shortly after noticing this, the ignition auto start problem reoccurred.

To get the instrument panel out on this model you have to disconnect the speedo cable AT the Transmission.

The next experiment was to just disconnect the speedo cable at the transmission and everything returned to normal!

There is an electrical connector on the left side of the transmission right at the point where the speedo cable goes up into the tranny.

It has 4 connectors, is about 2 inches long, about 3/8 in wide. Could this be the electrical connector that is causing the issues?

What is this connector? There is a smaller cable harness leading from it going back a little. I am not sure where this leads as it goes over or into a plate that is about 6 - 8 inches behind the tranny. ... Maybe the catalytic or oxygen sensor (??)

Anyway, I would appreciate any further assistance or advice. (I also have to wonder if this is the source of the car cutting out over the last year going around corners? i.e./.: a chaffed wire shorting or broken cable/connector? ... although everything looks like it is OK)

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Don

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'90 300SL
'90 190E 2.6
'87 300TE (gone to car heaven)
'84 190D (passed along...still in the family and used on a daily basis)