Adding to what the Mod says.
You should have a check that the cause is not a virus on your computer.
Or any sort of malware.
A few weeks ago i had to go and look at some ones computer because it was doing exactly the same thing.
It turned out that a Bitcoin mining program was the cause as a background task.
Using about 70% of his processor time to remote mine for bitcoins.
Im careful, but some how it managed to get on my machine also, Everything went to a crawl including loading web pages. But knew by then the cause.
There it was mining away using 70% cpu utilization on my system.
Please click on this link and download the free version.
Install it on your computer, and run the program.