I have read the previously posted threads about it without a clear solution. My sonos (sound bar) is connected to my cable box via optical audio cable, we have noticed now it randomly comes on late night playing the TV output. We normally just turn the TV off and go to bed, not the cable box.
It’s weird that it decides to connect to TV on it’s own when not directed via app. I don’t have alexa connected to sonos and i don’t believe there is an alarm set in sonos app.