Folder with a question mark appearing on my Mac sometimes

If the issue is persistent, try reinstalling the MacOS from recovery.

More information and further troubleshooting steps can be found here on this link

If your Mac starts up to a question mark - Apple Support (CA)

If the question mark is persistent, and your Mac does not start up normally:

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 notebook computers that have Touch ID, press and hold Touch ID.
3. Use Disk Utility to repair your startup disk. Follow the steps for a Mac with an Intel processor.
4. If Disk Utility found no errors or repaired all errors, reinstall macOS.
5. If you still need help, please contact Apple Support.

Is this the Article the user is referring to

If your Mac starts up to a question mark

A folder with a flashing question mark means that your startup disk is no longer available or doesn't contain a working Mac operating system.

If the question mark is persistent, and your Mac does not start up normally:

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 notebook computers that have Touch ID, press and hold Touch ID.
3. Use Disk Utility to repair your startup disk. Follow the steps for a Mac with an Intel processor.
4. If Disk Utility found no errors or repaired all errors, reinstall macOS.
5. ➡️ If you still need help, please contact Apple Support. ⬅️

6. Have the computer evaluated by the Professionals who have the Special Hardware Software and Expertise to diagnose the issue and offer possible solutions

7. - Make an Appointment at the Apple Genius Bar and have them evaluate the computer

According to the article, "A folder with a flashing question mark means that your startup disk is no longer available or doesn't contain a working Mac operating system.“

It's not necessarily that everything is missing. It is sometimes just a single file that it can't locate. It may be indicative of some corruption in the drive. Make sure you have a back up. You may need to reinstall the OS.

It's been a while, but I think sometimes an NVRAM reset would repair the problem.

Can you show us a pic capture of the folder with the question mark?