My 92 500E has something similar. It sounds like a rattle/squeak from the A-pillar or maybe behind the passenger air bag. It is intermittent and can be very annoying. I have not been able to sort it out. I have not spent much time trying to figure it out as it requires riding in the passenger seat while it squeaks/rattles. I intend to spend some time on it in the next few weeks...

I would appreciate any suggestions that you or anyone has....

Thanks!

TWB