It definitely sounds like your TV is failing its initial hardware check, but before you assume the worst, have you tried disconnecting all HDMI cables and the Ethernet cord to see if an external device is causing a CEC conflict during the boot process? Also, does the red LED blink in a steady rhythm, or is there a pause between the sets of four flashes, which usually points to a very specific voltage issue on the power board? I spent hours dealing with a similar "black screen of death" on my old display, and I discovered that sometimes a simple firmware re-flash from a thumb drive can bypass the error if the OS has just become corrupted. I managed to find the full technician's breakdown on Manual Machine https://manualmachine.com and it was a total lifesaver because it listed every single blink code and the corresponding part that usually needs replacing. You should locate your specific Bravia model on their site and look for the "Service Manual" rather than just the "User Guide," as that's where the deep diagnostic secrets are hidden. I recommend checking the section on "Forced Factory Reset," which often involves a very specific timing of the power button that isn't mentioned in the basic consumer paperwork. If you can get it to stay on for even a minute, you might be able to run the self-diagnosis tool from the hidden service menu. Give that a shot and tell me if the blink pattern changes at all after you pull the power cord for a while.