My iPhone is an SE. A couple months ago it started having an issue with turning off. I would turn it off, the screen would turn black, then a few seconds later the Apple logo would flash back on and off constantly until I plugged it into the charger (which it would then continue to the lock screen but never turn off). It used to happen occasionally but now it happens all the time and I have not been able to fully turn off my phone for over a month. Could this be a power button issue?