Diagnosis
This is almost always triggered by an external device waking the TV via HDMI-CEC (Anynet+), or by the TV's own auto-update/power-saving settings.
How to Fix It
Go to Settings > General & Privacy > Power and Energy Saving.
- Turn off Auto Power On After Power Failure.
- Turn off Auto Power Off (this can sometimes cause a wake cycle).
- Go to Settings > Connection > External Device Manager.
- Disable HDMI-CEC (Anynet+) entirely as a test. If the random ons stop, you can try re-enabling it and turning off the specific setting for each connected device that might be sending a wake signal.
If That Didn't Work
Perform a full power cycle: unplug the TV and the One Connect Box from the wall for 2 full minutes. Also, check if you have a SmartThings routine or timer accidentally set.
Heads Up
If you disable HDMI-CEC, you'll lose the ability to control connected devices (like a soundbar) with the TV remote. You'll have to weigh convenience against the ghost-in-the-machine issue.