Sounds like "death wobble". I have a '13 Equinox with electronic steering, towed it for the first 3 years without any issues with the steering. The wobble is created by sharp turns such as pulling out of a side street, and the only way to stop the wobble is to come to a complete stop, and then proceed. You don't make many friends on the street this way.
I have to remove a fuse to tow the car which also kills the electric to the steering which obviously effects the unwanted wobble.
As previously suggested on this form, I wrap a bungee on my steering wheel and hook the two ends on the front edge of the driver's seat to create tension on the steering wheel to keep it centered, it does not take a lot of tension to stop the problem.
My Equinox is a 4 cylinder which has electronic steering, the 6 cylinder engines have hydraulic steering which is not prone to wobble.
I've towed the last 11,000 miles(approx.)in this manner.