Wont turn on. Keep restarting with Apple Logo

Hello!

The iPhone 6 keeps in a restarting/booting loop. Shows the Apple logo for a few seconds and the restart again. And again, and again.

I try those things:

1) Go to DFU mode and try to restore with the iTunes:

a) Get several times the error 9 (and try all the solutions in the web)

b) Some times the process go trough, the phone works fine for a couple of hours and then go back to the initial problem (apple logo, reboot, restart, loop)

2) When it in the middle of the loop: Take apart the iPhone, disconnect the screen, connect again and then the phone boot ok. Work for a few time and go backs to the error again.

Any ideas?

thank you so much!

Federico from Argentina.