You haven't got a Sonos CR200 have you? To phase them out Sonos started to implement annoying bugs, one of which was to trigger the current playlist to start at random times. Mine used to start at around 4am on the Play5, which is loud! Sonos blamed it on cats jumping up and pressing buttons on the controller.
The other thing is Spotify, are you sharing Spotify accounts? Spotify can control your Sonos remotely. Before I had Spotify myself some friends were round and one added his account details to start a playlist. The next morning (early) when we were asleep, we were awoken to the house shaking. He had tried to listen to some music on his headphones and when not hearing anything, turned up the volume, up and up, not realising he was still connected to our Play5 miles away! Scared the **** out of me
Oh, and another cheap Sonos deal......
www.hotukdeals.com