Power Down on its own

[sm0125]

Recently, my phone has been powering down on its own. this happens when i am actively talking on the phone or when its sitting idle. At this very moment, i was listening to Pandora on the phone and the screen has blackened out. My notification light is blinking green. the Power button is not responding and the I have already taken out and put back in the SIM card and the SD cards. Is there any resolution for this or do i need a new phone.