Hei,
check your springs, perhaps you have a broken spring (very normal in W124) you can adjust the car height with the rubber cushions on top of the spring. there are 4 alternatives (different thicknesses). They are marked on the side with small bumps. 1 bumps means the thinnest cushion, 4 bumps is the thickest. You can adjust that amount of height with these cushions. Due to the geometry, the car rises about the double as the difference of the new and old cushion thickness. The spring has to come of, so you need spring compressors, (use only MB ones, because that is dangerous). It might take a few trials to find the correct height.
There might be other issues, hope not.
regards, Tomi