There are trip-points in your steering that release the stick once you turn your wheel back tire straight after a turn.
You should be able to HEAR when it trips, and there are quite a few points. To hear all of the points, hold your keep holding the signal stick to on as you straighten for a full-lock turn. When you do, you should hear a number of clicks or small thumps as you hit the trip points.
If you hear nothing? Someone screwed up inside there somewhere or for got to attach some trigger, or whatever it’s called.
Normal trips are not activated with small lane changes on a highway though. Only if a turn spins your steering wheel a good bit off of straight, etc.