Try this first. Since your wife has the same type handset, try swapping batteries to verify if it is the phone or the battery.
The cell phone is only 10 months old, babied, never wet or dropped. It started intermittently now it's full time. Can't find any help from AT&T either on e-mail or phone. Wifes phone (duplicate) working fine, bought same time. I see from a Google search that others have similar problems without resolve. Help