I never get sleep paralysis in bed at night. It only ever happens if I doze off during the day, usually somewhere unusual like at work.
I had a boring job for many years where I just had to be in the store, and sometimes it was very slow. I would doze off in my chair, knowing it was a slow day and we had a door buzzer to alert us anyway if someone came in.
When I would fall asleep like that, my subconscious worry of someone coming in and catching me asleep would kick in and I would dream that I heard the door buzzer. In the dream I would try to get up and be ready, but completely unable to move. Sometimes I would dream a customer coming, or hearing the phone ring. And every time I would fight to open my eyes.
While having this struggle I would realize that not only could I not open my eyes, but I couldn't even move my body or breathe. So then I would start trying really hard to do one of those, sometimes fighting to lift my arm, or turn my head, or just struggling to breathe.
It always seemed like an eternity of struggling to snap out of it. And eventually I would wake up, sometimes hyperventilating because I was trying so hard to breathe but was actually doing it just fine without knowing. It also seemed as though I could see my surroundings, but I'm not sure if my eyes were open or that was part of the dream.
But every time I woke up like that, there was no customer in the store, no missed calls on the phone or anything. I had dreamed the part that woke me up, but with no other recollection of any other dream besides being there in the store.
Sometimes, when I heard the door buzzer, I would wake up just fine and deal with whoever came in. Eventually I realized that the actual door buzzer would wake me instantly with no problem, but the one I dreamed never did.
I don't really have these episodes anymore since leaving that job and no longer having the opportunity to doze off during the day. But every now and then it happens if I take a nap on the couch or someplace else during the day. I think it's my subconscious trying to stay alert to things around me when napping at odd times with the potential to be interrupted.