when i unplug my sony lcd tv off it sometimes wont start up whats wrong?.

I have a 50 in LCD TV thats about 3 years old and when I have my tv i turn it off wait until it shuts down and drag it off the wall and when I plug in my tv wont start up again. . . sometimes it takes a day or so to actually turn on does anyone know whats wrong with my TV. . This is like the 4th Time their help would have happened to crazy?