I have the same (or similar) issue with my Samsung Odyssey+ WMR headset. At random time intervals the headset displays go black and when I check the application window (that usually mirrors the headset display as two circular pictures) these are frozen up too. It usually unfreezes after a time (sometimes a few seconds, sometimes nearer a minute).
I’ve tried with and without the openxr preview enabled, and with old and new NVidia drivers. Nothing seems to make a difference.
My PC specs: Ryzen 3600, 32gb DDR4, M.2 SSD, NVidia 2060 GPU (asus rog strix).