Replying to SamsungGill - I have cable box ran to HDMI 3 on tv (tried HDMI 1 with same issue). I have xbox one x ran from HDMI to HDMI in on Q70 soundbar. HDMI ARC from Soundbar to HDMI 4 (ARC) on Q70 tv.
What other devices are connected to the television and soundbar?
This same thing is happening with our new TV and it's not okay. We've left the house and come home to the TV on a random program that is not appropriate for our 7-year-old son. We have nothing connected to the TV, only the wifi.
The TV will only power on by itself when HDMI-CEC or Anynet+ is enabled and a connected device is sending a signal to the TV. The TV receives this signal and powers on. Most likely culprits are a cable box or satellite box, but can also happen with connected sound systems or blu-ray players.