I hate to be the bearer of bad news to you, but my '92 300SE was/is doing the exact same thing. Revereve will eventually go out, and sooner than you think, but the forward gears will work great. I have had a bunch of knowledgeable folks look at it and the concensus is that something called a 'squash plate' is almost gone. When it fully disappears you will no longer have reverse. This happen to me in a matter of days. The best I can find is about $1750US to have fixed.
Good luck and let us know what happens in your case.
Mark
Good luck and let us know what happens in your case.
Mark