I am no MB expert, but yellow brown trans fluid? I'm from the old school and yellow brown was not good back then. I agree as stated above change fluid and filter. But also the first thing that came to my mind, was ice build up under car restricting the trans linkage. Just a thought. Good luck

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Stable:
1973 450sl
1978 red diamond ice vette
1975 steel blue convertable vette
2002 steel blue dakota quad.