Recently I've noticed my i5 10600k running at very low clock speeds, it used to stay at its base clock of 4.1Ghz but I now see it dropping and hovering sometimes around 790Mhz/0.79Ghz. Not sure why it's doing this and I've looked into a few other discussions about people with similar issues, but no luck.
Also fairly recently the CPU has been pushed to 100% usage and can stay there for quite a while, with weird windows apps/programs running at high CPU and power usage.
It sounds like your system is overheating. The 790Mhz is an indication of ProcHot which is a thermal throttling extreme event. Download hwinfo and look at the CPU temperature. If it does end up being the CPU temperature you should be able to remove your heatsink and re-apply the thermal material or consult a local shop that can do that for you.
That seems a little complicated for me to figure out lol, but I have also noticed that when this problem first started happening I have had random apps all of the sudden using a crazy % of my CPU. Like all of a sudden Chrome using 80% or other apps using way too much than usual. This also causes the temperature to increase.
As I was watching my CPU more I also realized that when it does drop to a low clock speed it does boost/turbo right away back up to 4.47Ghz when it needs to.(When a work load comes along)
So maybe this is normal?