So, “why does my Frenchie shake,” you ask. There are two varieties of this behavior: involuntary and voluntary. Either way, whenever your Frenchie shakes, he is responding to a sensation (physical or emotional). Watching his body language will assist you in determining the cause of his shaking. After a while, you will know, intuitively, what the trouble is, and when (and how) to apprprpriately intervene.