Why am I suddenly twitching/spasming while waking up?

For the past almost month i have noticed when I am waking up in the morning my whole body is doing a weird twitch or spasm thing? If you’ve ever experienced falling asleep and then suddenly feeling like your falling and jerk awake, that’s what i am experiencing but without the falling feeling. It’s so weird because im still asleep but in a light enough sleep where im conscious but eyes still closed, so i’ll keep doing it until i just get up. The only lifestyle change i’ve had since this has started is taking a new antidepressant auvelity and lowering my dosage of lithium. I’ve tried looking online but I can’t find an explanation. I have an appointment with my med manager next week so I will definitely bring it up but I wasn’t sure if anyone else has experienced this as well?