All Sony TVs feature a standby light, which is used as an indicator of when the TV is powered on or in standby mode. The light can also indicate a problem with the TV if it is flashing in an abnormal way.
Check the lamp cover if your TV is a projection set. When the standby light flashes three times, it indicates that the lamp cover is loose. Reattach the cover to fix the problem.
Let the TV cool down. Four flashes on a projection set indicates that the TV is overheating. Check that the vents on the set are clear and not too close to walls or other obstructions.
Perform a power reset. Turn off the TV, unplug the power cord and let the TV stand for 60 seconds. Plug the power cord back in and turn on the TV.
Connect the TV directly to a wall outlet if you are using a power strip. This will let you know if the problem is with the power strip and not your TV. Also try plugging it in to a different power outlet.
Update your TV's firmware, if applicable. Some Sony televisions can receive updates to their internal firmware that will add new features and fix bugs. Refer to your TV's User's Manual or look up your TV's model number in the Driver & Software section of the Sony support page. (See Resources)
Perform a factory reset. With the TV on, press and hold either the "Reset" or "Up Arrow" button on your remote, depending on the model of your TV and remote. Press the "Power" button with the "Reset" or "Up Arrow" button held. The TV turns off and back on. Release the "Reset" or "Up Arrow" button.
Contact Sony support for service. If none of these steps works, your TV will need to be sent in for service repairs. (See Resources)