The possibilities are too many for turning off itself.
1) It could be a heat issue with the TV set
2) It could be a software issue with the TV set, for example energy saving settings or active stand by mode.
3) It could be a timer set up in the TV set menu.
4) It could be a faulty power supply.
5) It could be a very unstable mains supply (not very likely, but possible)
You can check the user manual for information about +"TV power on control (Active Standby)"+
Sometimes the LED's on the front of the TV may indicate "the issue":
Just reset the network and try for WIFI issue:
To connect to a wireless network, perform the following:
- Press the "Setup" button on the remote.
- Use the up/down arrows to select "Network".
- Use the left/right arrow buttons to enter "Network Setup" and change the settings from "Wired" to "Wireless" if necessary.
- Select "Wireless Setup" and choose "Assisted Setup" from the available options and press the "OK" button on the remote.
- A list of available wireless networks will display, select the one you wish to connect to and press "OK".
- Select "Security Key" from available options and press "OK".
- Enter the network password for the wireless network you are connecting to.
- Once the correct password is entered, select "Done" and press "OK".
- Select "Done" again when prompted on the next screen and press "OK".
- The TV will connect to the network.
- Once connected, the screen will return to the "Network" menu.
- To perform a network connection test, go to the "Network Setup" menu and select "Network Connection Test" to verify the connection.