I've had this in combination with sleep paralysis. Also my most panicked dream ever.
Basically I woke up in sleep paralysis, and then thought I had broken out of it when I had really just gone back to dreaming. It was my first time having sleep paralysis so I didn't know how to react.
The third time it happened my friend was there. Then I remembered I had already woken up twice and might still be dreaming. I had read about lucid dreaming and "reality checks" so I did a check with my hand and realized I was still dreaming. I had been wanting a lucid dream, but because it had been a nightmare so far, I got the coldest shiver down my spine as I looked at my friend, realizing "you're not real". I followed him into another room and confronted him. "You're not real". He gave me a super creepy smug stare and then suddenly im a split second he lunged at me, his mouth opening a meter wide as of he was gonna eat me in one bite.
I woke up drenched and out of breath, but I was nonetheless relieved to finally be awake.