Happening to me this evening on v188.8.131.521.*
4 times in the past hour or so. Checked for devices, nothing unknown in them (have seen that before where an unrecognized device name was showing up in my account incorrectly with Spotify claiming ignorance of it being their fault)
Just happened a 5th time while typing .. I had the About window open so I could get the version number, and the help-> about screen suddenly faded away and volume dropped to zero. less than 7 minutes from previous occurrence.