I know this sounds weird. I've had two intermittent rattles. One was caused by the metal clips for the dashboard cover plate, located at the end of the dash between it and the front passenger door. I fixed that using cloth tape on the metal clips, as per various suggestions I saw on this forum.

 

That left one other intermittent rattle that seemed to come from the centre and also the passenger side of the dash (yellow arrows in the pic below).

 

Now, here's the weirdness: Me, my wife and anyone who has been in the car with me was absolutely definite about the location. Its 100% coming from the dashboard. BUT IT WASN'T!

 

I finally located it. It is coming from the handbrake. The rattle from the dash appears after I have used the handbrake a bit in stop start traffic or hill starts. The rattle sound is projected forward in such a way that you are absolutely definite it is coming from the dash. 

 

My temporary fix is simple. When I hear it, all I have to do is push the handbrake handle slightly left or right with my finger (as per the red arrows below). Then I have sweet silence.

 

Now I'll have to figure out what part behind the handle  is doing it - if anyone has dealt with this before, I would love to know what you did?

 

Yes, I get the exact same problem albeit very intermittently and yes it does sound like it is coming from the dash area funny enough.  No major fix that I can offer as it normally disappears on mine if I just hold and press the lever, a bit like you do.  If this doesn't work I also press the button on the handbrake itself and that makes it go away.  It can disappear for months though and seems to be temperature related also i.e. more noticeable in the hot weather.  I think it is the metal part rattling/buzzing against the leather and the leather is reacting to the heat, expanding and contracting creating a slight void between the metal and leather casing - well that's my theory!  Used to get it much worse on a Octavia years ago and then one day it disappeared completely.