Random freezes, pointer moves, no response to clicks

Why is my laptop freezing?
Screen randomly freezes, I can move pointer but no response to clicking. Cannot alt-tab through windows. This happens in firefox and chromium. Ran memtester, all ok. Set FF to erase data, memory when closing, cleared memory & data, increased files open (ulimit -u) to 4096 when I saw the error message: too many files open - still freezes. (It just now froze as I was typing this message!) It can freeze after one minute or 30 minutes. Must hold power button to force off. Same happens in Ubuntu and Mint. System Monitor shows that FF never uses more than 1.5% of cpu and there are no other processes using more cpu time. One clue is that shortly before it freezes moving the mouse will start highlighting every line it passes and will only un-highlight by pulling the cursor back, and cannot stop any further highlighting. Must force reboot to get back control.
Firefox 106.0.1
Chromium 106.0.5249.119

Laptop Make: Model > Framework: Laptop AB
OS: Pop!_OS 22.04 LTS x86_64
DE: GNOME 42.3.1
Kernel: 6.0.2-76060002-generic
Shell: bash 5.1.16
WM: Mutter
CPU: 11th Gen Intel i7-1165G7 (8) @ 4.700GHz
CPU Usage: 11%
Disk (/): 15G / 220G (8%)
GPU: Intel TigerLake-LP GT2 [Iris Xe Graphics]
GPU Driver: i915
Memory: 3008MiB / 15785MiB (19%)
Resolution: 2256x1504