Phone keeps crashing

Over the past few days, my phone keeps shutting off, and will only turn back on after I plug it in. It’ll be fine until I lock it, and then it won’t turn back on, and I have to plug it in again. It doesn’t always happen right after I lock it, sometimes I can get back on it, but usually can’t. Yesterday it would not turn on at all, the apple logo would pop up, and then it’d go black, then pop up, and go black. I backed it up, then restored and updated it. Restored it from back up, and it was up and running. Now today, it’s turning back off again all the time. I deleted ever app I possibly could off it, cleared all history and whatnot, thinking it might be a virus, or just a bug in the system. And it’s still happening.