Macbook screen start flickering

It's possible that your MacBook is experiencing a hardware issue that is causing the flickering and lines on the screen, as well as the black screen that appears after the Apple logo. Here are a few things you can try to troubleshoot the issue:

1. Reset the SMC (System Management Controller) and NVRAM (Non-Volatile Random-Access Memory). To reset the SMC, shut down your MacBook, hold down the Shift + Control + Option keys, and then press the power button. Release all keys simultaneously and then turn on your MacBook. To reset NVRAM, shut down your MacBook, and then press and hold the Command + Option + P + R keys while turning on your MacBook. Hold the keys until the Apple logo appears and disappears twice.

2. Try booting your MacBook in Safe Mode by holding down the Shift key while turning on your MacBook. This will load a minimal set of drivers and prevent third-party software from starting up. If the flickering and lines disappear in Safe Mode, it's possible that a third-party app or driver is causing the issue.

3. Connect your MacBook to an external display to see if the issue persists. If the external display works fine, it's likely that the issue is with your MacBook's display.

4. Contact and take your MacBook to an authorized Apple service provider for diagnosis and repair.

Keep in mind that attempting any kind of repair or troubleshooting on your own can potentially cause further damage to your MacBook. It's always best to seek professional help if you're unsure about what to do.

Hello katiushka272,

Your Mac shows an Apple logo when it finds your built-in or external startup disk. As startup continues, you should see a progress bar. If your Mac is stuck on this screen, we recommend trying to resolve the issue by following the steps here: If your Mac starts up to an Apple logo or progress bar - Apple Support

We think you'll find these steps helpful:

If your Mac is stuck on this screen or keeps restarting

If startup never progresses beyond an Apple logo or progress bar:

1. Press and hold the power button on your Mac for up to 10 seconds, until your Mac turns off.

2. Every Mac has a power button. On laptop computers that have Touch ID, press and hold Touch ID.

3. Turn your Mac back on. 

4. If the issue persists, press and hold the power button until your Mac turns off. Then unplug all nonessential accessories from your Mac, including printers, drives, and USB hubs. You could have an issue with one or more of those devices or their cables. 

5. Turn your Mac back on.

6. If the issue persists, once again press and hold the power button until your Mac turns off. 

7. Repair your startup disk as described in How to repair a Mac disk with Disk Utility.

8. If the issue persists, reinstall macOS from macOS Recovery.

If you need help, contact Apple Support.

Thanks.