Hi there

A couple of things you can try

1 - Unplug TV power cord from the wall, and disconnect all other devices connected to your TV except aerial cable, and turn TV on again.

2 - If step 1 fails, ensure you are using the latest firmware.

3 - If step 2 fails, perform a factory reset.

4 - If step 3 fails, it probably indicates a hardware failure on the TV, go through Sony Support to get your TV repaired.

Hope that helps.