how can i fix my 39" lcd television ?

how can i fix my 39" lcd tv thats made by universal media corporation , the televisions model number is 39/63g (or as quoted on the rear of tv in full) 39/63g-gb-3b-ftcu-uk , the tv also has a product: ( code as stated in full on rear of tv )uw39c63bftcug527 , the tv was working fine until recently when it switched itself off and now once you turn it on it stays on for any random amount of time from a few minutes to ten to fifteen minutes when it switches itself off , does anyone know what the problem may be or how i can possibly fix this problem myself

GLYN
January 2016