SHARP 29" TV switching off to Standby

Question

Hi. I have a SHARP TV about 8 yrs old that switches off to Standby mode after using for about 20-25mins each time. Then it could not turn ON and stayed at Standby mode (even using remote or just push OFF then ON button - still back to standby mode). After about 15-20mins later I could switch on again by either using remote or push button. I checked all timer functions and there are no timer or lock that activated at all. Everything was as before. It just has this trouble of switching off and stay at standby mode after 20-25minutes of usage. Is this something that can be solved easily? What are the likely faults? Please advise.