Is it the power supply or the firmware? When I got my 50" Sony 7+ years ago, I noticed it would occasionally"reboot," (that was my interpretation, but in other words turn OFF and the turn ON again withing a few seconds) but ONLY within the first 10 minutes of being turned on, and, again, only occasionally. However, after some months from day one of my using it, the TV NEVER AGAIN exhibited that behavior for the remaining 6+ years of use. The TV was ALWAYS connected to a UPS from day one, so buck and boost protection was present. Also, I was careful to download any updates to the firmware while Sony "supported" the TV.
I had always assumed it was a software/firmware problem and COULD likely be fixed with an update that Sony would provide for maybe a year+ of TV being put on the market before Sony would abandon me
. Also, is your Sony defaulted to turn itself OFF after so many hours of activity. The Yamaha receiver I got about the same time had many reports of the unit just turning off for no apparent reason, even in the showroom. I got the unit anyway, and discovered that Yamaha factory set as DEFAULT that it turn off the unit after 4 hours of of last activity. I thought it was STUPID of Yamaha to do this because it would likely confuse people who would think the unit is defective. I believe what was being reported as a defect by those on the boards at the time were witnessing the defaulted power off, especially those who saw it happen in showrooms. I, of course, did NOT change this setting because I liked the unit shutting itself off if I forgot to do it when leaving the house or fell asleep. I should add that I also have the Dish H3 set to go to standby in 4 hours time, as well. So, I have a triple threat, but at times it really has saved me from having the things on needlessly when something has come up and I think I will get back to TV watching, but things turn into a 3+ hour mess--even when I am inside the house and can't get back to TV watching until bedtime. I also like that the stuff turns off if any of us forget to do so when we have to leave for the entire day and evening.
I will tell you that over the years my TVs (which I have set to 4 hour power off mode, as well) and AV Receivers have auto powered OFF when I was present and viewing at times because I was watching content that did not require me to send any commands to either unit or I was away for an unplanned hour or so. I did not happen a lot, but it has also happened to dear old mom when she had been watching content. She just never had a need to send a command to ONE or all three devices: Dish H3, Samsung TV, AV Receiver. But she calls me to say her TV or AV receiver has turned OFF and she wants it back on PRONTO! This would happen like 1 or 2 or 3 times a year, at most, but it can happen.
One trick I do is to always set the volume command (like form the Dish, as one example) to the TV and then let the TV send the signal to the AV Receiver because that will prevent the TV from powering off, and it will reset the TV for the next 4 hours before auto power off because it is receiving a volume command while the AV Receiver is also receiving the command from the TV that causes it to also reset for the next 4 hours. Otherwise, the TV will go to sleep every 4 hours (the time I have chosen) because it has received no commands. I know, others have set things up differently, but I LIKE all 3 devices to shut off after 4 hours of no commands in case I forget to turn them off for a long goodbye or I fall asleep.