Fix 1: When YouTube Music on your phone pauses automatically, you should first consider checking the status of your phone’s Internet connection.
Fix 2: Disable the Low Power Mode on iPhones and Battery Saver Mode on Android.
Fix 3: Background App Restrictions on mobile phones are settings that limit the activity of apps when they are not actively in use. So you need to close it.
Fix 4: Make sure you use the latest YouTube Music version.
Fix 5: Fix the YouTube music playback pause issue by deleting the file that is causing an exception in the app’s music playback service.
Fix 6: Insufficient storage space can also cause unstable application operations. Please check and clear the storage of your phone.
Fix 7: Disconnect and reconnect your Bluetooth device.
More solutions here: