10-15-2012 03:19 PM
10-16-2012 05:47 AM - edited 10-16-2012 05:48 AM
This sounds like a hardware problem so you'd better take it for service, simple as that.
I have owned two 9900 models since it is available and never experienced what you are describing.
Is it new or second hand? What about the battery?
10-16-2012 06:14 AM
10-16-2012 04:27 PM
Described as you explain, this seems very odd indeed ...
Have you tried to eliminate any "exotic" software (third party applications that may cause the OS to act randomly)?
I would encourage you to do it and/or to restart from factory configuration / initial settings (don't forget to backup your data first!).
Did the problem begin after a specific installation or any particular manipulation from your side?
Check also the battery contacts and if it does not "move" inside the phone.
If none of these checks solve the problem, I would bring it back for service under warranty if this is a new device.
Hope this helps