I am having the same thing -- it just started yesterday and I haven't been in my phone since.
I spent an hour with a chat rep who told me the phone wasn't charged enough to do a factory reset.
I took it into the store tonight and they told me that there was nothing they could do; I would need to buy a new phone. Very frustrated!
There was no trauma or un-locking of the phone on my part; I restarted the phone and it never recovered.