This is happening to me. Well, since I "updated" to 4.4.4, the phone simply continually turns on and off, on and off. It's been doing it for an hour. I tried doing factory reset really quickly, and also tried booting to Recovery mode, and then when I go to the "Recovery" option, it simply goes black. No dead android appears and I have no chance to Hard Reset.
Is my phone bricked or something? I had unlocked bootloader, but never actually rooted it, but my warranty is now void anyway.
Anything I can do or am I just screwed?