Have you tried the shock test of pushing each fender down hard a few times and see if they come to a pretty abrupt stop? Compare your rebound to another simular car? The old gas mercedes cars seemed to be really shock sensitive. Shocks can wear out partially or totally inside without leaking a drop. Have not had bad shocks yet on any of my 123s so do not know if they are as sensitive. You will probably get a better opinion but if car is bouncing and rocking after going over a bump bad shocks are going to be pretty well at top of the list I think. Your springs are probably aged a little but do not have anything to do with the problem other than giving you the bounce etc. that is their function to do. At least it still rolls well? The absolute test is you needing a neckbrace to drive the car after the shocks totally fail. Of course we are all well aware they should last to 500,00 miles but some just do not seem to make it. Sell the old ones on ebay as they are not yet at their 1/2 life point. If you are lucky the car is going to drive and feel so much better when you eliminate the bad shocks you may wonder if it is the same car. The bad shocks have most likely been gradually failing for quite a period of time I imagine.(years) Plus better tire life to boot. There should be a shock (s) link in search function but for my money would buy the brand you mentioned. Regular or heavy duty your choice. Try to make sure country of manufacture is germany if possible. Really if you want any more specifics of testing or whatever just drop another note on this site. Also excuse me having a little fun as the last time I had bad shocks it bounced my brain a little too much.