My first 9810 did the random boot thing big time. Almost right out of the box. Got it replaced under two weeks from purchase. Almost no similar issues since then. I did start to have the problem again, to a much lesser degree, after an OS upgrade. A reinstall of the OS fixed that.
Originally Posted by burninbob433
Back up your apps and data and try either a reinstall or an upgrade. If you want to go for 7.1, go for the upper .2xx builds or .3xx builds. All pretty solid, AT&T hotspot without tethering. Anything .4xx and up loses untethered hotspot and multiple locations have mike muting issues on AT&T.