iPhone Boot loop stuck
Many things can cause a boot-looping device. 

Try these things (if you haven't already) to see if anything helps:


Try a hard reset (Home &amp; Power button for 10 secs)
Use a genuine Apple Lightning connector
Use a genuine Apple charging brick and let it charge overnight
Try to connect it to different computers (mac/pc if possible) with an updated iTunes
Put the phone in recovery mode (search DFU Mode). Careful, this can reset your data 
Use 3uTools for putting it in and out of Recovery Mode
Use 3uTools to flash the firmware (you can't downgrade)


If you are comfortable opening your device (now that it's out of warranty) then consider the following:


Disconnect the Front Camera Ribbon from the logic board and reboot
your phone
Disconnect the screen assembly completely and see if iTunes will recognize the phone.


Otherwise, you may have a logic board issue. If you are uncomfortable doing these steps, consider either doing an OOW replacement at Apple or finding a reputable, independent repair shop to do the troubleshooting. A shop that also does micro-soldering can go deeper if the problem is not modular in nature.