Reset NVRAM or PRAM on your Mac
If your Mac has issues related to settings stored in NVRAM or PRAM, resetting it might help. Sound also comes under this section, so I strongly suggest you to try this as after reboot your MacBook is getting normal.
How to reset NVRAM
Shut down your Mac, then turn it on and immediately press and hold these four keys together: Option, Command, P, and R. You can release the keys after about 20 seconds, during which your Mac might appear to restart.
- On Mac computers that play a startup sound, you can release the keys after the second startup sound.
- On Mac computers that have the Apple T2 Security Chip, you can release the keys after the Apple logo appears and disappears for the second time
When your Mac finishes starting up, you might want to open System Preferences and adjust any settings that were reset, such as sound volume, display resolution, startup disk selection, or time zone.