My 2015 IS 350 had an issue similar to this. It was almost the opposite though. It would stick when I started to turn. It was generally on long sweeping turns at freeway speed, after a long straight away. It was very unnerving, because it would resist the turn in and then “snap” loose when I applied more force to get it to turn, which then caused a little over correction.

Took it to the dealer, they drove it a few miles and then tried to tell me it was the lane departure alert...my car did have the LDA, however, it was not the auto-steering kind. All it would do is beep if I crossed a lane marker. It did not ever beep when I experienced the steering problem, and it wouldn’t have caused it anyway. This was one of the few times I felt like I wasn’t getting the “Lexus” service experience. That answer showed a complete lack of familiarity with their own product and was honestly just lazy.

I ended up turning the car in at the end of the lease, steering issue still there. Maybe the next owner will see this and get Lexus to swap out the rack...