Moving from not having any remembrance of a flashback/being triggered to sensing something is a good thing. It means you are beginning to heal. Your brain wouldn't be allowing you to begin to realize this is happening unless it knew you were ready for it. However, if it continues excessively, you may be going through memories too fast in therapy and need to slow down and not cover so much material at a time.

Body memories as some call them, are very real and can be strong. Try to allow it... to "allow" it and not panic but tell yourself it is something from the past and isn't happening now. Do grounding techniques and center yourself.