Lexus SC430 2002 model: lost control of steering wheel twice, basically the steering wheel free flows in both directions without any impact on the tires. Is this a common problem? What could be happening?
Your opinion is greatly appreciated. Thank you

 

Sounds very scary. I cannot imagine an interim failure like that, but I would surely not drive the car even once after that. I have to admit I am skeptical. Not sure how you avoided a accident, unless you were at rest when this occurred. Please be safe.

 

Since the LS/SC430 use mechanically connected steering columns with power assistance, I would NOT drive the car until this is resolved.
Sounds to me like a spline is slipping out or similar. Get it checked ASAP!!