Hello, eno111
Welcome to the Microsoft Community.
Hi, sorry to hear about your situation. I understand how frustrating it is when your game suddenly runs at low FPS after your computer restarts. I will give you some general steps to troubleshoot some issues first, and you can report back after that.
- Update your graphics card driver:
Press Windows key + X, then select Device Manager.
Double-click "Display adapters" to expand it, then right-click your graphics card.
Select the "Update driver" option, then select "Search automatically for drivers."
Outdated or faulty drivers can cause low FPS.
You can also go to the graphics card brand's website to download the latest drivers directly.
- Disable fast startup:
Fast startup can sometimes affect game performance until you restart your computer.
To disable it, go to Control Panel > Power Options > Choose what the power button does.
Click "Change settings that are currently unavailable" and uncheck "Turn on fast startup."
Save changes and restart your computer.
- Adjust power options:
Go to Control Panel > Power Options.
Select "High performance" or "Balanced" mode.
Make sure your computer is not set to power saving mode, which may limit performance.
- Clean boot:
In order to check for interference from third-party software, you can run a game in clean boot mode to see if this problem occurs. You can refer to the following link to perform a clean boot:
How to perform a clean boot in Windows - Microsoft Support
Disclaimer: A “clean boot” starts Windows with a minimal set of drivers and startup programs. It helps to determine whether a background service is interfering with your game or program and to isolate the cause of a problem.
These steps of "clean boot" might look complicated at first glance. However, to avoid any trouble for you, please follow them in order and step-by step so that it will help you get back on track.
Best regards
Bobhe | Microsoft Community Support Specialist