My iPhone 6 keeps restarting

I was using my phone with no problems. I made a phone call and they didn't pick up so I sent a text with siri voice to text. I saw that I had like 3% so I plugged the phone in to the usb on my computer to charge it. As soon as I plugged it in it cut off like the battery had died. I saw the spiral circle, then black, then the dead battery icon, then black, then apple. Then after it is done booting up it flashes the lock screen and cuts off immediately starting back over with the spiral circle again. Repeat repeat repeat.... It never gets past the lock screen. I've tried holding the power button and the home button together to try and reset it. I see that doing that interrupts the cycle but it doesn't change anything. The flash that I get with the lock screen shows 1% battery and hasn't gone up at all. I've had the phone charging now for about 45 minutes with no change in the cycle.

Please help

PS. I've done every update that comes out when it comes out.