Lol I don't shake it like you do with a shaker. I care about the lens!
What I did is gently turning the superiour part of the lens in circles while the bottom stayed approx. at the same place. The movement is .. 'conical'?? Sorry, lack of english vocabulary
Well, I'm reliefed that I'm not the only one and thus, this would probably be normal.
It would be interesting to see what serial numbers do make that sound and which don't.
I'll modify the first post later on to reference all the lenses.
Anyone interested in such statistics?