TrustedInstaller is basically used by a service called “Windows Module Installer” which is used to install Windows system modules. The system modules include Windows Update and Automatic Updates which automatically scans your system to check for any new updates and hotfixes available. So when scheduled Windows Update is performing its update scan or check on your system, the TrustedInstaller.exe process increases the CPU usage.
So if you spot high CPU usage for trustedinstaler.exe process, it might be that Windows is looking for or updating your system via Windows Updates.
To prevent high CPU usage, users are often recommend to turn off automatic updates in Windows. You can change this functionality using Group Policy as mentioned here: https://www.kapilarya.com/avoid-windows-updates-automatic-download-windows-10