How to find out the cause of the system's wild brakes, including windows and even the mouse cursor?

Question

Malware

A few days ago I discovered that suddenly, for no reason at all, the system began to slow down wildly, right down to the mouse cursor and windows.
I also found that when opening the task manager, such brakes disappear, and in performance you can briefly see how the CPU usage drops from 60-80% to the usual 2-7%.

Answer 1

At random I can come up with two equally probable reasons:
1) a virus. This is hinted at by the loss of load when opening the task manager and the spontaneous closing of the task manager.
2) Windows services do something in the background. For example, disk indexing or something else.
But I'm leaning towards the first option, so CureIt or any other antivirus + cross your fingers in the hope that the virus will be detected and cured.

Answer 2

Try Process Explorer .
There it is easy to see who loaded the system the most at any time in the interval of a few minutes ago.

I see what loaded me 2 minutes ago