1993 BMW Shakes

This is my first beamer. It has High Miles 210k. I I bought it in Salt lake and drove it home to Boise, which is about 350 miles away. When I turned it on the next day it was shaking in park. When I put it in neutral the shaking whent down a little and in drive it gets worse. Could it be that it needs an idle adjustment? If so, where is the adjustment knob?
Sam