c240 Automatic - problems when revved

So how many miles are on the car now?
You should have the transmission fluid level checked and see if there is leakage around the electrical plug to the transmission. You'll need to check for codes. A bad MAF can also make strange things happen.
The vibration you feel may be from worn motor mounts or transmission mount or a combination of both. B

That all depends on what the problem is. Did you do a scan for codes?
It could be something as simple as a loose wire or vacuum hose. I'd be suprised if it needs the mounts at 70k but guess it all depends on how well treated the car was by the last owner. You'll have to start by doing some DIY inspection work inside the engine bay and underneath the car. Check all your fluid levels especially the tranny fluid. You can also inspect the throttle body/air filter. There are many good write ups on how to clean them. None of these items will cost you anything for now. Like I mentioned before MAF's are a very common problem but until you can verify something its all guesswork and that doesn't work on Benz's. B