hi,
it sounds like you maybe had a hypnagogic or hypmnapompic hallucination? one means "seeing things just when you're about to fall asleep" and the other one is when you're just waking up, but i can't remember which is which.

they're incredibly common and a lot of people have them, and there's nothing to be worried about either. some people see tigers pacing around their rooms, or i use to see a toy aeroplane flying around mine.

sometimes changes in meds can cause these to happen more frequently, as our bodies adjust to it. also, being excessively tired, stressed, having a cold/flu etc.

nothing to worry about, but if it continues & still bothers you, mention it to your doc!