Does he have a micro-SD card installed. If yes this has to be formatted in the phone.
Save all data and format it through the settings menus.
Also, if he is running some 3rd party apps that may cause this you can try to run in the
safe mode. Turn off phome, turn on, whem you see the moto logo hold down both volume
keys until you see the safe mode sign below. This turns off all 3rd party apps. If the system
is stable like this it means that the culprit is one of those apps.
Also, you can clean cache. Download the App Cache Cleaner from the market and run it.
Good luck,