XPS 13 9305 - massive performance loss, CPU max 8%, 0.2 Ghz

Suddenly a week ago I recognized that my XPS laptop (13 9305 from 2021) is not usable anymore. I had not used for some days, but would have recogniced this massive lag when it was present time before.

I tried mostly everything to find out what is wrong with no success, for instance from MS community (“My pc got slower but CPU usage is low”). In Task Manager I see constantly a max of 8% and 0.2 Ghz on CPU (see screen below), no peaks, always on full 8%. The system went unusable with this.

Situation is, observations are:

• Windows 11 is fully updated, version 24H2. „Dell Command | Update“ and SupportAssist do not show available updates, apps are also should be updated.
• Removing 3rd party Anti Virus does not solve.
• Dell hardware diagnostics show no problem, neither SupportAssist nor from BIOS.
• Changing Windows Power Mode for max performance (on power usage) does not solve.
• When started in Safe Mode (or in WinPE from USB) problem is not available.
• In BIOS I loaded default settings.
• Reinstall Windows 11 as “Inplace, keep personal files and apps” does not solve
• Complete fresh install Windows 11 (24H2) with blank system SSD does not solve.

By now I restored a backup from three weeks ago, hopefully it can be solved without having to fully setup my whole apps and settings again.

I’m not in DELL support plan anymore, am willing to get paid support, but do not even know if I better choose hardware or software support. And how software support can work as I don’t think remote access will work with the limited system performance.

Thanks a lot