Unhook the fan and see if the set works, it will work without the fan for testing purposes, chances are the fan is drawing to much current and is being shut down by the TV circuitry
Either the lamp is on it's way out or..... the lamp is incompatible because it is not a original one. (ie the same as what they fit in the sony factory)
HELLO, IT SOUNDS LIKE THE LAMP IS GOING BAD, THE PART NUMBER ON THE LAMP IS A XL-5200, VACUUM THE FANS ON THE BACK OF THE SET, DO NOT USE CANNED AIR!!!! THAT CAN BLOW DUST INTO THE OPTICS....TKS