Reset SMC by following the directions applicable to your MacBook Air here ➔ How to Reset SMC. If that does not solve things then-
Reset NVRAM/PRAM by following the directions applicable to your MacBook Air here ➔ How to Reset NVRAM/PRAM.
Enter ➔ Safe Mode and see if the screen issue still exists in Safe mode. Log out of Safe Mode and then reboot computer. If that does not solve things then-
Finally if none of the above works then you can enter ➔ macOS Recovery Mode and reinstall the macOS and see if that solves it.
Reset SMC by following the directions applicable to your MacBook Air here ➔ How to Reset SMC. If that does not solve things then-
Reset NVRAM/PRAM by following the directions applicable to your MacBook Air here ➔ How to Reset NVRAM/PRAM.
Enter ➔ Safe Mode and see if the screen issue still exists in Safe mode. Log out of Safe Mode and then reboot computer. If that does not solve things then-
Finally if none of the above works then you can enter ➔ macOS Recovery Mode and reinstall the macOS and see if that solves it.