A previous poster mentioned this issue and I'm having the very same thing happen to me (I would've replied in that thread but the site was not letting me do that for some reason...and it could be user error). Twice since 11 a.m. today after I activated the phone the Moto X has powered down on its own. The latest time the battery was at 53% so I don't think it's attributable to that. Growing increasingly frustrated. Any ideas...suggestions? Thanks in advance.
Fully Charge it of you haven't, If you installed any 3rd party that have bad or not very good Reviews on PlayStore keep that in mind and you might want to Run the phone in Safe Mode.. Or perform a System Cache Clear.
And on the Sim Card was it fully seated into the phone and at any time was the gold Area of the Sim touched by fingers if so that can have an affect on the phone). Sim Cards and the Oils and Static Electricity in our finger don't Mix well..
If you continue having issues Don't go Past your 14 days for Returning it, you might try another Sim be careful handling it I stress this again as it is a Vital part of what helps the phone Work..
I was the previous poster with the rebooting issues. I haven't had a reboot in 2 days that I am aware of, although the phone was rebooting when not in use and it is difficult to monitor it 24 hours a day.
My first reboot was with the device fresh out of the box, I had just set up accounts and was working with the moto migrate app. It would be highly unlikely that a third party app would be causing the device to reboot in this situation.
It is also unlikely that handling the sim card could cause damage to the card which would reboot the phone. You can physically remove the card and the phone will continue to function. The cards are also highly resistant to static electricity. That is not to say that it is impossible to damage one, just very difficult.