I feel like I am experiencing something similar. It's been happening for nearly three years now. I'll be sitting or standing and suddenly it will feel like the floor jerks sideways under my feet. My whole body does the startle response to try to regain balance. I've absolutely face planted on the floor from the chair from overcorrecting. And the floor is definitely not moving, I checked 😁
Also when I'm tired now, things will appear to be moving in my peripheral vision. It will look like my glass of water is falling over or my pen is moving or whatever. And again the startle response kicks in, I've knocked over the things I was trying to save from falling that were a moment earlier perfectly fine.
I hope that it stops for you!
💜💜