I go through this sometimes when talking with my therapists about the past and it has gone away on its own. Basically what is happening when I go through it my body reacts the same way it did during the event. reliving it which is called a flashback. I shook then so I shake now. Once I desensitize (talk, journal draw create it with clay so much my brain gets used to the fact that it happened) myself from the experience I no longer experience the flashback (past shaking)