This is a very recent problem.
I'm pretty convinced it was caused by a recent software update.
I'm currently running Linux Mint 21.2 Cinnamon.
The problem is that soon after starting up my laptop, the cpu fan starts to run fast, creating a lot of noise.
By running top from a terminal: $top -d 10
I can see that the cpu is working hard, even though I'm not asking the laptop to do anything.
By reading some chat on the internet, I found I could stop the cpu & fan from going crazy by putting it to sleep (Fn + F12 on this machine) and then I could wake it up and it was fine!
I remember seeing some microcode updates and I think this may be at the heart of the problem.
For now I'm happy to do the sleep/wake thing each time, because I'm curious to see whether a future update will fix it!
...watch this space.