Ball joints cause the squeaking
Common problem with s-class especially with high miles. the ball joint boots crack and water gets in them from car washing or road, etc. No lube = creeking sound. Not sure about the other problem while driving could be the same thing not sure. But the symptom of getting in the car and the car squeeking coming from the front shock areas is ball joint lube problem. MB has a tsb on this. Just get you ball joints replaced and get a new alignment, warranty might cover it.