I had a similar problem with my 190D (similar suspension system). Turned out, the rear cross member had rusted through, allowing one of the links to break free. It could be that, or a similar problem with the camber link itself, LCA or axle half shaft. Either way, it's just work. About all the only special tool required might be a spring compressor. It will be obvious when you pull the wheel. If she had stopped when it began vibrating, it wouldn't have been much different.