"I was having this problem whenever my battery died completely. Whenever I plugged it in it would automatically turn the phone on but there was not enough battery to get through the boot process and it would die again.. and because it was still plugged in, it would try to turn on again before it was ready.
Whenever this happened, my solution was to connect the phone to my laptop or computer for a few hours. It would charge much slower, but for whatever reason it would not automatically try to reboot.
I would wait for it to get to about 50%, then switch to the wall socket and let it do its ""optimization"" thing."
"Short of removing the battery, which is not supported with this device, the only other thing you can do is let the battery drain completely, so that the power button will not activate the screen. Then, plug it in with a high-quality Android charger (in my opinion, the one which came with the phone stinks, so don't use it). I used a charger cord from my old OnePlus One. This eventually did the trick. After about an hour, the phone was at 25%. I was then able to turn it on normally.
Hopefully, this drastic measure works for you as well...."
I had mine in one like an had to flash new firm ware an rom on it get what you on I think it MDX website they have stock rom or special one to took me a while because I never done it before an it works as good as new an right after got it up the updates for it came from blue and it was updated to marshmallow hope this helps you.
