Have you checked around the white trim area, where the interior mirror / sun roof control switch is located ?.
When you hear the rattle, apply light pressure with two fingers to the white surround.
I had a rattle in my car that was driving us mad !.
I said it was on her side, she said it was on my side !.
My wife nailed it one day, it was the trim I mentioned above.
Give that a go !.
The other common noise, is a ticking / creaking noise between the front screen and the top of the dash panel.
This has been covered in another post, windscreen wiper hard rubber gasket rubbing on the glass !.
A few people have this issue, more notable when the weather is cold and the cabin is ingested.
When the cabin is warm, the ticking / creaking is a lot less.