Hi Charles,
I don't know how's the battery health status of your iP5c, but be aware that, when batteries are reaching the critical point of their life, often they have unespected or unpredictable behaviors.
It never happened to my devices, but, just to try and explain your problem using my experience here in this forum, often dying batteries can act in a weird way (unfortunately sometimes they also completeley die without giving you the time to make a backup, and that's why I always tell users to create a backup of their data on a regular basis, at least twice a week).
So, my suggestion is to have your iP5c inspected as soon as possible.
Regards
Giulio