From this week, my MBP M1 Pro is very slow, almost unworkable
Resolution
Reset NVRAM & SMC
Force the MacBook Pro M1 to shutdown suddenly by pressing Power button for 10+ seconds
Close the lid for 30+ seconds
Start it normally
Blow the vents to CPU fan
Yep, use any thing that could create strong air flow to blow it, like your month.
The vents are located between the screen and the main body of your MBP
Remove Grammarly from OS accessibility
Go to System Settings -> Privacy & Security -> Accessibility, remove apps like Grammarly (but not Zoom as you may still need it for remote controlling)