My iPhone shuts itself off after a few minutes

It started cutting off and on randomly & I powered it off For and hour and it still cuts off by itself and when it come on it only stay on for like 6 minutes and cuts right back off ! And I have clicked my volume up and down button and held my power button and it went black and when the apple logo stop up like always I let go and it stayed on for a little longer but after went back off !

[Re-Titled by Moderator]