CPU render time issue

Hello everyone and thank you in advance for your help.

First of all, my config.

Intel i7-9700K
GTX1660 6GB
Ram: 16GB at 3200

So, I have a problem with Call of Duty Modern Warfare.
My CPU render time has become unstable, it spikes to 80 ms....
How can I say that my FPS drops sharply because of this... (10 or even 5)
The temperatures are good and consistent.
And when I check the task manager, my CPU is running at 24% (Modern Warfare window minimized)

For your information, everything was working fine before, and I haven't changed anything in the game's graphics settings.

Thanks again in advance for your help.
Have a good day