Hello Harry,
Welcome to Microsoft Community.
In your description of the problem, I noticed that you mentioned a key point where you see strange lines on your screen.
I'm guessing you might see something like the screenshot below:
Considering that your screen can appear black under moderate or heavy load, I recommend that you manually download and reinstall the drivers and firmware packages for your Surface Laptop 7 as a priority:
Download Surface Laptop 7th Edition from Official Microsoft Download Center ****
After the installation is complete, restart your Surface and see if the same problem reappears. If the problem persists, please refer to the information in the support link below to try UEFI and then test your screen:
Troubleshooting options for a screen that has lines through it - Microsoft Support ****
If you notice the same problem again in UEFI, it's proof that there is a real problem with the screen, and you may need to take it to the Surface support team for inspection or repair.
Since your Surface still seems to be booting, let me share with you how to connect with real-time support from the Surface tech support team through the Surface App:
Open the Surface App (usually built into your Surface device, or you can download it from the Microsoft Store if you don't have one) and follow the procedure below:
- Click "Help and Support" and then click "Get Help".
- Briefly describe your problem in the text box, such as "The Surface Laptop 7 screen will go black and strange lines will appear", and then press Enter.
- Click "Contact Support" at the bottom.
- Select "Technical Support" and click "Confirm".
- You will see "Chat support" or "phone support" options, please contact them during working hours, you will get one-to-one support services.
Surface Live support can guide you through creating service orders if necessary.
That's all I can share with you as community support, and I hope this process helps you.
Best Regards,
Mitchell | Microsoft Community Support Specialist