Hi,
Do you have this problems from the beginning?
First you can do a factory reset, but if you have important data, make a backup first, because this will erase all your personal data.
[guide|23217]
This will resolve your problem if it's from an application or settings.
Do a SW update.
If you have same problem after this steps, then the problem is HW.
From your explanation I thing you can have a problem with the camera, but I can't be sure.
Regards.