The following steps are designed to help you troubleshoot the issue methodologically
1. TV Auto Standby is set to 240 (default)
By far, this is the most common reason why most customer reports that their TV turns itself off after sometime.
By default, Philips TV is set to turn itself off after 240 minutes of no interaction (if there's no signal, it will turns itself off after 10 minutes)
To change this behavior do the following:
Go into professional menu (Press Mute, Left Right Up Down OK)
Go to Advanced-> Auto Standby = 0
2. TV is being turned off by the connected device via HDMI CEC
External devices connected via HDMI can sometimes send command to turns the TV off/on
To change this behavior do the following
Go into professional menu (Press Mute, Left Right Up Down OK)
Go to Sources -> EasyLink -> EasyLink = Off
3. TV schedule is turning it on and off
Go into professional menu (Press Mute, Left Right Up Down OK)
Go to Features-> Features - > Scheduler
Check if any of the schedule is turned on
Also Date and Time -> Time Zone Settings-> to ensure the Time zone is set correctly