This issue im going to describe is VERY dileberate when it happens….at speeds over 30mph the car will almost seem to glide right with a feel of floating almost like the ass end is riding high and all the suspension has been released its almost is like a hinge feeling i feel like it has to be something with the gyroscope or stability control or something the action is way to dramatic than that of bad busings or falied sway bar, is it not? 110,000k original suspension parts the rest of the vehical has been taken care of at every turn by BMW Seattle and just went out of full warrenty
Without looking at it my thoughts would be alignment or tire issue. A busted belt may not be clearly visible but would cause this issue. A quick affordable test would be to rotate both front tires to the back and move the back tires to the front. Then test drive and see if any difference can be noticed.
Dynamic Stability Control
The Brakes Electronic Stability Control uses two steering wheel angle sensors and wheel speed sensors to control braking. I do not think that would cause the issue you are having.
On slippery surfaces or during aggressive maneuvers, if the vehicle understeers severely, the computer will actuate the brakes on the inside rear wheel, just hard enough and just long enough to correct the steering behavior. When the vehicle oversteers severely, the system will brake the outside front wheel instead.
NOTE* When Servicing this system, OEM may require the angle sensors be calibrated to the vehicle thrustline.