Anyone know about hypnogogic or hypnagogic hallucinations?

I found out online that what I’ve been experiencing all my life are hypnogogic hallucinations.
About an hour after I go to sleep I wake up and either see/hear/smell something that at the time seems very real to me. I found a blog page (cannot relocate) that said people who have “alien abductions” have these. I do not, but frequently see someone “watching” me (thru holes in ceiling, or a/c vents, or whatever but all up near or in the ceiling), as well as assorted other items like waking up in a “strange room” that is really the bedroom but “different”. Seeing people or angels, my dog that passed away recently, hearing music or smelling cigarette smoke are others.
These can be very frightening and lately are happening more than once a night, disturbing my sleep.
Anyone else have this experience?