I would suggest trying a few things to narrow down the cause of the display problem.
1. Check the display in UEFI
Shut down your Surface Studio. Press and hold the Volume Up button, then press and release the Power button. Keep holding Volume Up until the UEFI screen appears.
Check whether the lines or other display abnormalities are visible there as well. This will help determine whether the issue is related to Windows or possibly the display hardware.
2. Try an external monitor
Connect your Surface Studio to an external monitor and check whether the picture is normal. If the external display works perfectly while the built-in screen shows lines, the problem may be with the built-in display assembly or its connections.
3. Check recent Windows and graphics updates
Have a look at your Windows Update history, particularly any recent Intel Iris Xe or NVIDIA graphics driver updates. Microsoft has released updates addressing display flickering and graphics-related TDR issues in the past, so it is worth checking whether the problem started after a particular driver or firmware update.
4. Run Surface diagnostics
Open the Surface app and check whether your device has the latest drivers and firmware installed.
You can also follow Microsoft's official troubleshooting guide:
What to try if your Surface screen is flickering, distorted, or has other display issues