Why does my iPhone 4s sometimes automatically turn off?

[iMore Question]

why sometime my iPhone 4s is automatically turnoff?

I don't know why, sometime i open one of the application in this phone like Facebook, after 10 minuets or 20 minuets i use this application my phone is automatically turnoff, and after a few second my phone is turn on. I don't know why.

 

[Dream_king]

Re: why sometime my iPhone 4s is automatically turnoff?

Which iOS your phone is using?