Hello,
Welcome to the Microsoft Community.
May I know the current situation? You mentioned that the screen gradually goes black, and I assume that you could operate the Surface before the blackout.
You can perform a clean boot and start in safe mode respectively to confirm whether the same problem occurs. This helps troubleshoot if the issue is caused by third - party software or driver failures.
How to perform a clean boot in Windows - Microsoft Support|
Windows Startup Settings - Microsoft Support
Best regards,
Huy-K | Microsoft Community Support Specialist