Wish I had a firm answer, but a few thoughts: 1. make sure you don't have "sleep timer" enabled; 2. you may want to call Sharp tech support---they were very helpful when I had early questions; 3. I too have had this problem when running apps like You Tube and can't help but wonder if it's overheating. Looking forward to more knowledgeable answers, but I see you posted over a month ago with no response.