Q: iPhone 6 keeps restarting while charging

My iPhone 6 was dead so I plugged it in to my computer to charge. Now it keeps restarting itself without fully turning back on. It doesn't seem to be holding any charge. I've tried unplugging it, but it is still is saying it needs to be plugged in.

I've tried plugging the cord into a different port in the computer and that doesn't seem to do anything. I've lost the little adapter that plugs into the wall so I am not able to do that. I've charged it with this computer plenty of times with no problem, but it has never been completely dead before.

iPhone has most recent software update.