It was Thursday. Microsoft releases OS updates on Thursdays. I got an OS update (Win 11), noticed degraded performance in the form of CPU hitches every 7 seconds, task manager showed the GPU dropping to zero, then coming back up to the 70-ish percent it normally runs at. The graph looked like a roller coaster.
Restarted the computer, ran Windows Update. Intel graphics driver update available. Downloaded/installed. Rebooted.
Problem solved.
Check for CPU/chipset/MOBO hardware drivers and see if that works.