I had the same problem with the wobble under similar conditions to the OP. We have a 2015 Chevy Malibu. I was sure that something had broken on the coach or the car. I pulled to the side (in a construction zone) and could not find a problem. I slowly pulled back on the road and carefully increased speed. There were no further problems. I didn't think to look in the rear view camera as I was concentrating on getting to the side of the road safely. The Malibu does have electric PS.
Dave
07 Revolution 40E