Automatic Shutting off???

Could either be the firmware or the hardware. Suggest you take it down to the Nokia Service Centre to let them flash a new firmware for you, then if it still doesnt work, let them repair the hardware for you. Things to note are to backup your data, your contacts, messages or anything you would like to keep for your phone to your computer before you bring it down as updating the firmware will erase the phone's memory.

mine was doing that, tpoo it in and got a new sim card. old card wored great in old phone but not the new one. they gave it to me for free. just take it to you store and have them look at it.

Hi, Mine is Nokia 5110 and I am also experiencing the same problem. I am at loss what could be the reason.