A few things to check right away
How can I fix high CPU or disk usage by Ntoskrnl exe. in Windows 10?
Recently I ran into a strange problem: a process named System (NT Kernel & System) was constantly using about 15 to 30 percent of the CPU on my Windows machine.
In the above screenshot, System is using 0 percent CPU, which is how it normally should be. The System process basically houses the kernel and driver code plus system threads and is an essential Windows process. Do not attempt to kill or remove the process.
Before we get into the technical details, this issue is usually caused by a bad or outdated hardware driver in Windows. There are a few things you’ll want to check right away:
