Since BIOS and Safe Mode display correctly, the most likely cause is the normal Windows display driver or display mode after startup.
Try this in order:
- Reset the graphics driver when the screen goes dark.
- Press Windows + Ctrl + Shift + B.
- If it works, the screen should flicker or a beep may occur.
- Cycle the display output mode.
- Press Windows + P, then press P again and press Enter.
- Repeat a few times to cycle through PC screen only / Duplicate / Extend.
- This helps if Windows is sending output to the wrong display mode.
- Boot into Safe Mode with Networking and roll back or update the GPU driver.
- Open Device Manager.
- Expand Display adapters.
- Right-click the GPU and select Properties.
- On the Driver tab, select Roll Back Driver if the issue started after the driver install.
- If rollback is unavailable, select Update driver.
- If rollback/update does not help, reinstall the display driver.
- In Device Manager > Display adapters, right-click the GPU and select Uninstall device.
- Select Attempt to remove the driver for this device, then Uninstall.
- Restart the PC.
- Open Device Manager again, right-click the display adapter, select Update driver, then Search automatically for updated driver software.
- Check hardware connections again.
- Reseat the HDMI/DisplayPort cable on both the GPU and monitor.
- Try a different cable or a different monitor input.
- If available, try another GPU output port.
- If the issue began after a recent change, use System Restore.
- Boot into Recovery Mode.
- Go to Troubleshoot > Advanced Options > System Restore.
- Choose a restore point from before the issue started.
- If Windows still loses signal only in normal boot, test from Safe Mode to isolate the driver.
- Safe Mode loads only the minimum required drivers and services.
- If video works there consistently, that strongly points to the installed graphics driver or related graphics software.
Also note:
- A blank screen with a blinking cursor can indicate that UEFI/BIOS cannot find a boot device, but that does not match this case because Windows begins loading.
- If the problem started after a display driver update, rolling back is specifically recommended.