Random High CPU Load occurrence is slowing down the Mac.

This is some kind of hardware problem. The system is detecting a fault and using kernel task to throttle the system.

If you have any external hardware, disconnect it. This can be caused by something as small as a usb dongle for your external display. If the problem continues with no external hardware, you will have to take the computer to an Apple Store or Authorized Apple Service Provider for diagnostics and repair.

Unfortunately, I can’t read your EtreCheck report. The web forum software is blocking it.

My Mac is very hot right now.

That may be why it is slowing down. kernel_task is spiking to throttle the cpu to cool it down.

We may be able to offer more help with more information. So far we do not even know what your mac model is.

Please run Etrecheck and post its full report here. Use the "additional text" button and paste the report into the text box.

The system drive is FULL. This is not good. It is always recommended to have at least 15-20% free but you have only 30 out of a 500GB drive.

The system cannot work properly. Try to make some space and see if that helps. Also, you have system security updates turned off. But make space NOW. If it still continues then there may be a hardware issue, as etresoft suggested, but maybe it’s the full disk drive…

kernel_task runs much of the processes and also is used to throttle the cpu when it gets too hot.

Does it feel hot to the touch when this happens?

How can I know why my Mac is heating up so much ?

I was wondering about that, too.

On your video, it shows WebKit GPU running high cpu % for a short time. Do you have lots of Safari tabs open?

The overheating could be caused but the accumulation of dust/pollen/smoke particles in the fans and on the heat sinks preventing proper cooling.

Get the insides of your Mac cleaned.