Another way to be sure if you have self-levelling suspension and you are not to mechanically inclined: look at the stamped plaque near the engine bay hood lock that has a bunch of three number codes (or the production data card of your car).

If the lists includes code No. 480 (Self-levelling suspension on the rear axle) or Code No. 214 (ADS-Adaptive Damping System), your car is equipped with such a system.

A. Rosich
S320, 1998
E320T, 1995