SONY KDF-E60A20 TV

SONY KDF-E60A20 TV was new 10/25/2005  The TV turns on like normal but after a minute the screen goes black..After a minute, the screen comes back on as if the set was just turned back on(picture dim for a second and then gets bright as normal).  Then after a minute it goes black again.  This continues to cycle like this over and over.  When the picture is on it is a very good picture.  I hope you can help.