No. Reinstall powerplan is not a solution, mere a workaround.
5800x ? What
The information is to vague, but Your processor is running way to hot, 70C and how do You know this?
By just looking at a temp just now? The CPU temp can varies multiples of thenst in just a couple of seconds and can be very hot extremely fast.
Seems it could very well be that the inbuilt safe protection is shutting down or at least lower its frequencies.
Dust is clogging the exhaust cooling fins? Common cause.
Is it a laptop or a desktop?
Please specify the computer name and model nr.
If a special build, specify motherboard and model nr?
CPU model nr?
If You don't know, please use the free Specyy and make sure to un-check any 3-third party s/w during installation.
There are a small "Customize" button just below the Big Install button. Make sure to untick everything there.
Then under File menu > Save as textfile > upload the information in Your next post.
So perhaps others can provide some help.
Best regards from Sweden