Hi and welcome to the forum.
Sorry to heard you're having this issue. Have you noticed any issues with Bluetooth as well?
If so, unfortunately it sounds like you might be experiencing an issue that has popped up quite a bit lately since the AT&T firmware update to 4.5.141. I don't know if it's coincidental and due to the age of the phone (though it's still young) or if the update has caused it, but I don't know if a user fix.
Do you still have warranty coverage on your phone? If so, you might contact your carrier or Motorola about service.