Given the age of your vehicle we would not expect it to be suffering from condensation of this nature, so assuming all the windows and sunroof (if fitted) are closed overnight, it is likely to be caused either by a leaking seal or a mechanical leak such as the air conditioning. We would suggest checking the carpets throughout the vehicle as this may give some clues to where water is getting in or leaking from, but you may wish to take the car to your dealer to be inspected.