Why is my Nikon D3200 misting up?

I bought a new Nikon D3200 but since using it have on two occasions had problems with fogging inside the body. It doesn't appear to be on the lens itself as it quickly clears if I remove the lens. I'm not shooting in particularly humid or damp environments: both times I was indoors. Does anyone have any ideas what may be causing this to happen, or whether the camera is faulty?

Added (1). Just to add: neither of the times the fogging occurred had I moved from a cool to a hot/humid environment or vice-versa. I was indoors on both occasions when the 'fogging' appeared.

Added (2). I live in the UK - we have no need for air-conditioning!

No, the camera isn't faulty. This happens when you take something from an air conditioned environment out into a hot day. It is a situation to be avoided. This article may help.
http://www.the-digital-picture.com/Photography-Tips/Cameras-Humidity-Condensation.aspx

No aircon? Moved from indoor to indoor? It's obviously a difference in humidity. It still is possible even in the same house or building. That is after all the cause of fogging.

Keep the camera in a sealed bag or box with a bag of silica gel. When you want to use the camera in another room, carry the box and open it in the next room.