You can follow the following steps to troubleshoot your TV:
Restart the TV and check if the issue is resolved. Turn off the TV and unplug the AC power cord (main lead).
When using a TV with the Self Diagnostics option, try the Self Diagnostics test.
If the above mentioned steps do not help to resolve the symptom, the product may require service.
As a Sony product owner you can contact Sony directly to arrange reliable, cost-effective out of warranty repairs through professionals at Sony authorized service centers. Getting your Sony TV repaired can be a bit expensive.