w124 e320 wagon rough ride

Ok, my wagon has almost 200k miles. the rear is especially stiff- when going over bumps i hear a loud thumping/ knocking; it is not overly bouncy on the highway like my w123 wagon was when it needed new sls accumulators, it's just really harsh. oh, and it's worse when the temperature is consistently below around 50- it seems to be a little more supple in warmer temperatures.

any suggestions?