W220life

I have a 00 S 500 with 136k and to my knowledge the original shocks and struts. The suspension air pump is new at 100k. When I accerate, or am on the highway, I get the feeling the car is sort of off balance or a kind floating feeling like it is trying to self adjust and cant. In the winter months the car tends to squat quite a bit more than normal. Has any one experienced this with theirs and what is possibly the issue?