It's just a window, not multiple (s)

I noticed this the other day when it was really cold (3C, I thought it was due to the temperature, but as it was a bit warmer this weekend (10C) I thought it may not rattle. It does......

To stop the rattle I can press my elbow against the glass and it stops. It doesn't rattle all the time just when on a bad road surface (which arround me there are lots of rubbish roads).

so any ideas what it could be??

Is it only rattling when the window is closed, or does it still do it when it's part/fully open?

Chris

it rattles when its closed and part open, not tried all the way down.....