Note some viruses monitor for task manager and will kill themselves if it is opened, then retrigger once it is closed. So if this is happening a lot then may want to look into that

I read that Windows reserves the excess CPU capacity, so when you open task manager it goes from 100% to whatever is actually being used. The strange thing is the PC seems a lot less stressed when I leave task manager open.

What if task manager also freezes?

Two weeks in switching from Windows to Linux and I never once needed to use the equivalent of Task Manager.

It may well have been beginner’s optimism, but still, it did feel strange, so strange indeed that I started wondering whether Linux Mint even had one and I got promptly reassured in my perception by the fact that instead of being named Task Manager (you act with it), it is named System Monitor (you observe with it).