Philip
I have same problem after changing my screen. Initially, phone would not power up after screen change, but unplugging the battery got it going again. Now it reboots just as you explained. One thing to add. I let it reboot until the battery died. When I pushed to power button it showed me a stable battery mode message indicating I needed to plug in phone. As soon as I plugged it in it went back into continuous boot mode.
Headed to repair store today.