Cpu usage has been exploding for a while, why?

I've been having CPU usage problems for some time now and am now at the end of my wisdom. No matter what I do, be it: gambling, text editing or just moving windows from A to B shoots my CPU load through the roof. When I play games that I already months ago, there still with old GPU, used Stottert and Stockt everything only because my CPU downright outrage. But since I always have a small control tool for CPU usage on the second monitor, I know that my processor did not even get beyond the 35% percent load and there was the SPiel and other streams on Twitch or something else on the second screen. Just when typing everything is quiet and the cores show a load of about 5-10% but as soon as I move the mouse just shoots the CPU load to over 40%! Only from the mouse movement.

And yes, I've already suspected a heat problem but my processors always stay below 40 ° C. I could not find any viruses, I use Bitdefender Plus.

Maybe someone here has some advice, or is my processor now too old and I have to exchange it for something more modern?

My PC Specs:

Interl Core i5 6600 (Skylake)
Palit GeForce RTX 2070 Super
16g Ram
Win 10

Maybe someone here has a suspicion or a solution, just because it all went some time ago with the same specs.

I use Bitdefender Plus.

make that time.

40% CPU load on mouse movement is normal if it's just a kernel. The mouse alone does not cause the 40%, the PC also does other activities besides.

Even if the off is, unfortunately, the same problem. I have also been using Bitdefender for just under two weeks, as it was recommended to me, but the problem now extends over months.

And with mouse movements, all 4 cores will then display between 25 and 40% utilization at once.

Did you reduce the number of active CPU cores, for example to 1?

How many cores does the task manager show, with performance and option, to show each core individually?