... depends what you are up to.
After all Yin Yoga with its body awareness and deep allowance and its deep opening of the hips seems to be one of the better ways to cope with trauma. But dont take me as an expert on that, I am only doing it regularly for a few weeks ...
When the shaking comes I would recommend to allow the movements to do what ever they are up to, just being aware of and deeply interested in it, you might even be able to enjoy them. After a few times you might want to let yourself completely be taken by your body. There might also be feelings coming up, ... just deeply allow them, also the resisting ones. Rest afterwards.
Make sure that your environment is safe so you cannot hurt yourself. You might also feel safer when somebody is arround.
Let your breath flow freely best with an open mouth. Watch, but dont control it, when it becomes faster, but make sure that you are breething and not holding it.
You also might find a TRE group in your town or a bioenergetic professionel who will accompany you through the process.
David Berceli has written good books about TRE and its mechanisms and there are also DVDs to show how to do it.
Here is another video just to encourage to trust your body:
Peter Levine created another body method which is well accepted called Somatic Experiencing. I read books about it but have not done it myself
Here is a link, where he greatly explaines the mechanism of contraction and decontraction with a slinky.
Hope that helps, and let us know how it goes