It's hard to know what is actually happening here, is the transmission slipping? Engine misfiring? Something else? I guess that is the question that needs to be answered to know what to do.
I would consider taking this to a MB shop and having a good tech go for a ride and see what they think it is. I would get the software in the engine and transmission control modules checked to see if they need to be upgraded, that could address this issue and you will never be able to diagnose this type of problem (software) yourself.
You mention a vibration, so it may even be a bad motor mount or something, but this is where the test drive comes into play.
Good Luck!