It sounds like a couple issues. The shake at speed could be tire related if it started right after the tires were installed, not uncommon for a weight to get tossed or slip sometimes. Were the wheels installed at the same time? If so, then I would check the balance and for tire runout as well. Some rims mount in a way that can make them act this way as well, they are the types that don't center on the axle hub and instead use the lug nuts to center, they can be touchy if they are not installed just right.
The side to side on a bump could be related to them installing the tires, if you have worn suspension bushings, raising the car during the tire install could have shifted them or even caused them to come apart so things can now shift. If you can get under the car, you could have someone push down on the car and watch the circled areas for movement other than just up and down rotation. I would suspect the track bar bushings more (in orange) but they all could do that. The motion could also be normal as the track bar will try to push the rear end sideways as it moves, but it shouldn't be really noticeable.
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Wednesday, January 5th, 2022 AT 1:43 PM