'''If ur IPhone is creating same problem like Turning off automatically, at anytime & reopens after hours then dude there's no need to be worry about your money and for your close to heart IPhone, lol !! Do follow these below steps '''
1- Your IPhone should have atleast charged or should plugged in .
2- Push down your Ringer button to Silent mode, i.e just push the button down in silent . (its weird but worth)
3- Press then hold your IPhone's power on/off button and Home button both at same time and for not just 10-14 sec. , hold them both untill Apple logo appears but don't hold for more than 1 minute
4- If doing above 3rd step your Iphone doesn't opens then friend don't worry do 3rd step simultaneously until and unless u see Apple logo .
And u can believe on this trick because friend when I was having IPhone 5s, I captured same problem and the only above solution made my IPhone to work as before, and tell u last thing this problem isn't temporary, ur IPhone will go dead several times but now u don't need to wait for it to reopen automatically
Just do the simple above trick
Hope u get ur solution