If you're de-casing the TV, you can see where the on/off switch actually wires into. It is possible it might even be marked on the board.
That said, If you're not going to do any soldering, you might want to research and see if there's a hidden menu in your TV that has any power-up after power failure type of options. Some TVs have service menus with additional options. My crappy magnavox doesn't, so I had to jumper the on/off switch (eventually put in a toggle). Some of my other TV's do have those power options though. It's a lot easier then soldering. Lot easier than arduinos.
Not sure my TV is as simple as two pins for the power on.
Most every function somewhere along the line starts out life as a single wire/circuit that gets jumped to a ground. There may be a lot of other crap in front of, or in back of it... but somewhere there's probably something you can solder into. Will it be easy to find?