Nokia 2365i / 2366i

The phone just shuts off about twice a day. It always has plenty of charge left and I am sure that I didn't hold down the END button or in any other overt way tell the phone to turn off. Yet it turns off. It's sorta ticking me off. To be completely honest, I have a tendency to play with the settings and *MAYBE* I just set up something wrong and forgot what it was. Does anyone know what I did to make the phone turn off? Is anyone else getting this with their 2366i? 😡