Why am I speaking gibberish when I wake up?

Hi, all. I've been having a strange issue over the past few years that maybe someone could shed some light on.

Full disclosure: I have severe depression, take medication for it and hear voices periodically. When I first started hearing voices I, like, went absolutely batshit and had a break from reality. I do not have schizophrenia or bipolar disorder... I've been diagnosed as simply having "psychosis." I am currently not being weaned off any drugs or am taking any new medication.

Here's the issue: for some reason, I wake up (like, I'm not half-asleep or groggy, I am conscious and know what's going on) and I start to talk gibberish and make jarring head movements. At first this really freaked me out but now I just let it occur because I want to understand why my body is doing this. I am not doing any of this consciously or on purpose. Er, yeah, I'm aware that this is most likely all due to my mental illness, but my cursory search on the internet did not explain my odd actions. Like, could it be a sign of schizophrenia or something else serious?

Thanks. Any thoughts are appreciated.