How to Reset Your Microsoft Surface Without Log into Windows

You can get to the reset option by restarting your Surface from the sign-in screen. Here’s how:

1. On your keyboard, press the Windows logo key + L. If you need to, dismiss the lock screen.
2. Hold the Shift key down while you select Power  > Restart in the lower-right corner of the screen.
3. After your Surface restarts to the Choose an option screen, select Troubleshoot > Reset this PC.

Ref: Restore or reset Surface for Windows – Microsoft Support