Dear easygoing,
Anxiety seems to be the answer when they cant find another reason :) Seems to me there are alot of anxious people running around these days..LOL.
Perhaps there is more than just Reiki at work? Reiki generally does not burn us out.
Grounding may work if excess energy is causing the shaking. It does not alter the effectiveness or depth of a treatment.
Hopefully there will be more responses forth coming for you.
Namaste,
holobon