I've never had a problem like this with my computer, but a TV that I have would work and then suddenly turn off. The only way to turn it back on was to lift the cable line or wiggle it around. Obviously, some sort of connection inside was messed up.
Eventually, it stopped working so I opened it up and didn't see a problem, but it worked when I flexed the mainboard. So, I just left the screws off the back (holding the board to the case) and every few months had to shove another piece of cardboard inside to flex the board more and get the TV to work. Needless to say, eventually this process didn't work so a friend of mine and I opened the TV again and played with flexing the main board while the TV was powered (bad idea) until there was a small explosion on the board. We then saudered the connection where the explosion occurred and amazingly the TV has never given me trouble since.