Hello, Sorry you're having problems. I need the following info to help:
1) What is the full model number off of the back of the TV?
2) Roughly how old is the set?
3) Are you saying it automatically turns itself back ON without you pressing the power button?
Thank you for the reply. This would be a fault in the TV's Mainboard- which is the AV processor and also the main processor of the set. It is literally the only board in a TV that can cause the set to actually power itself back on. On a user level the only thing you can try is leaving the set unplugged for several hours or more in the hopes that the processor resets. This drains all residual current from the TV. Beyond that, if the issue persists the Mainboard in the TV needs to be replaced. This is the board with the AV and HDMI Input jacks located directly on it and is roughly half of the cost of the TV when new to replace this part.
Replacement boards can be found on eBay and other used/pulled parts suppliers if this is something that you're looking to tackle yourself (use the model number off of the back of your set and the keyword "Mainboard" to search). Other than that I'm sorry for the bad news here and wish there were a quick fix.
If you need further assistance let me know. Before you go, PLEASE DO click at least a 3 STAR RATING, at the top of your screen. That is how I am credited for my efforts by the site. You can follow up any time as needed at no additional cost.