I'm running into this today. Brand new profile on clean install.
M1 Macbook Pro
MacOS 14.2.1
It seems to happen on pretty much anywebsite. I just had it happen here on orionfeedback.org immediately after uploading the attached movie to this post.
A page works fine for a bit, then suddenly appears to become completely unresponsive. Strangely I can still interract with the page, but there are no updates being rendered. Switching tabs or swithing to another window (or clicking the address bar) trigger a new render.
It's repeatedly happened here as well.