Anyone else have this issue? I upgraded my wife's 6 to 8.3 told her to kill it completely (as she hasn't done it in quite some time) she did,plugged her phone in the white background with the black Apple logo appeared (like it was powering on) however when she went to check if it was charged the phone wasn't on, just a black screen? After she removed the charger the phone powered on. I have never had this happen with any iPhone I've had, after draining the phone always turned back on after about 5-10 minutes on charge
If ever in doubt, enter Recovery mode by turning the phone off and holding down the Home button as you plug it back in to iTunes. If that fails, enter DFU mode. After doing either, do a full restore and see if that sorts it - if it happens again, of course.