interesting topic, i have the W203 (only had it a month) and noticed a few days ago that i started to notice the rear end 'going' at a relatively low speed, i obviously havent tried to replicate the problem as it has not been safe to try and investigate. the tyres do not seem to be in the best shape (although the tread is ok) which has already caused me concern so i guess its time to change them.
Any advice on what to get or anythign else that should be looked into? I will be changing all 4 tyres and getting aligment, etc... full works.