Fidgeting

I've noticed for several weeks that I've been having brief, recurring episodes that normally last a few seconds. I don't know what they are, but I'll have vivid memories that feel like some kind of flashback (though right now I'm reluctant to call them that); the memories consist of the accident that I had in May when I dislocated my knee. They change a lot but will always be centered around certain details during the event.

It just tends to either happen out of nowhere or it results from my mind wandering. Aside from my injuries, I've also had moments where I'll briefly remember embarrassing or unpleasant memories during these quick episodes. I pull myself out of them by unclenching and then clenching my fist. If the memory or thought is particularly distressing to me, the fidgeting will become more exaggerated and my hand will usually go into a 'claw' position.

Does anyone know what this is called? Or has anyone experienced something similar?