Since switching input devices briefly restores the mic, the most likely Windows-side causes are the selected input device state, microphone privacy access, input level, or the audio driver resetting.
Try this in order on Windows 10:
- Confirm the correct recording device is selected
- Go to Start > Settings > System > Sound.
- Under Input, make sure the intended microphone is selected in Choose your input device.
- Speak into it and watch Test your microphone. If the bar stops moving when the beep happens, Windows is no longer receiving input from that device.
- Check microphone privacy access
- Go to Start > Settings > Privacy > Microphone.
- Turn on Allow apps to access your microphone.
- Also make sure Allow desktop apps to access your microphone is On.
- If the problem happens only in one app, make sure that app is allowed there too.
- Raise and test the microphone level
- Go to Start > Settings > System > Sound.
- Under Input, select Device Properties.
- On the Levels tab, adjust Microphone and Microphone Boost.
- Test again under Test your microphone.
- Run the Recording Audio troubleshooter
- Go to Settings > Update & Security > Troubleshoot > Additional troubleshooters.
- Run Recording Audio.
- Reinstall the audio driver
- Warning: uninstalling drivers can temporarily remove audio input/output until Windows reinstalls them.
- Right-click Start and open Device Manager.
- Expand Sound, video and game controllers.
- Right-click each audio device and select Uninstall device.
- Select the box to remove the driver for the device, then choose Uninstall.
- Restart the PC.
- If Windows does not reinstall automatically, open Device Manager, right-click Sound, video and game controllers, and select Scan for hardware changes.
- Then right-click the audio driver and select Update driver.
- If using a Bluetooth headset or mic
- Make sure it is still paired and connected when the beep occurs. A disconnect/reconnect can look like the mic briefly works and then stops.
If the issue is with a Surface device, also check Start > Settings > Sound to confirm the desired input device is selected, make sure Allow apps and Windows to use this device for audio is allowed, try turning off Audio enhancements, and use Start test to verify whether the mic drops out during the test.