Diagnosis
This is usually caused by the TV receiving a 'Wake on LAN' or similar network signal, often from a software update check, or the HDMI-CEC feature (called 'AnyNet+' or similar on other devices) being triggered by a connected device.
How to Fix It
First, disable HDMI-CEC. On your TV, go to Settings > Display & Sounds > HDMI CEC Device Control and turn it OFF. Also, in Settings > Preferences > Power Settings, turn OFF 'Quick Start' and enable 'Sleep' after a period of inactivity.
If That Didn't Work
Unplug all HDMI devices when you go to bed for a night as a test. If the TV stays off, one of your connected devices (like a game console or cable box) is sending a wake-up signal.
Heads Up
Some router settings or network pings can also wake the TV. If all else fails, using the physical power switch on the surge protector or unplugging it is the only surefire way to stop it.