In a properly operating machine, "system" will not use very much CPU (< 3% over time).
If it is an issue, look at this Microsoft Article
Fixes for System High CPU
Key points:
- Update your drivers and BIOS/UEFI firmware from PC or motherboard
maker's Support Downloads web page, using the full model number,
Serial Number or Dell Service Tag on sticker. Compare the latest
drivers available for download with the ones presently installed in
Device Manager reached by right clicking the Start button. Make sure
you have the latest BIOS or UEFI firmware, Chipset, Display (Video),
Sound, USB3, Bluetooth, Network and all other drivers, or else
download and install the latest now.
Updating drivers from the Device Manager or Windows Update is rarely
enough. The most basic thing we need to learn to maintain a PC is keep
the latest manufacturer's drivers installed from their Support
Downloads web page.
- If nothing else works then do a Repair Install, by installing Media
Creation Tool,
https://www.microsoft.com/en-us/software-download/windows10
open tool and choose to Upgrade Now. This reinstalls
Windows while keeping files, programs and most settings in place, is
the most stable method to advance to the latest version, and solves
most problems
Another tool for locating processes that use CPU is SysInternals Process Explorer. I use this and it is very helpful