Mine has been doing that off and on lately, sometimes even when I leave it alone for a bit. At first I thought it might have been that it either overheated while I was using it or that it was a forced update from Barnes. But there have been no updates for months and it couldn't have been an overheating issue if it restarts while idle and no apps are running in the foreground. With mine, I think that it's approaching the end of it's life since my extended warranty will run out in November. As far as I'm concerned, B&N cheated their customers by selling poorly constructed/programmed merchandise.