That sounds like a firmware issue, I would connect your iDevice to iTunes on your Mac or PC, then restore it to factory settings.
If you need to keep your data, there shouldn't be any harm in restoring from a backup afterwards, however if the problem persists, try restoring to factory settings and not a back up.
Hope that makes sense, if you have any further questions, feel free to email me at nj.harris@icloud.com.