As most folks have already diagnosed, you have two distinct issues. The vacuum leak if causing your idle to surge as you described, and your worn motor mounts are the culprit to your vibration issues.
The vacuum leak is usually traced to one of the myriad of hoses throughout your engine.
After 4 1/2 years of enduring the idle surge, my indie solved the vacuum leak on my W124 and the surging has stopped. Now I have to bring it in for new motor mounts later as the vibration is now prevalent since the engine stopped surging...
