Has anyone ever experienced this, and knows what can cause this?

I was really tired this afternoon. I went to take a nap and within seconds I fell asleep and started to dream. The phone rang and I woke up briefly but heard my husband answer. I realized that my body felt extremely heavy. I was laying on my side and my left leg on my right felt so heavy but I didn’t feel like moving it. I quickly fell asleep again. In about an hour I woke up from a nightmare.

When I woke, I felt tired still and nauseas. I forced myself to get up because for some reason I felt I won’t wake up if I let myself fall back to sleep. I needed all my will to wake up. It must’ve taken at least 10 minutes to feel normal.
Can you fall into such a deep sleep that it would feel like you are dying? I’ve heard of sleep paralysis but it doesn’t seem to sound like this.

Or is it the nightmare was so intense and get my adrenaline going and leave me feeling shaken for a while? I dreamt that my son was coming to say goodbye permanently, as in forever.
I’ve never had this feeling after sleeping or even after really bad nightmares. Well, maybe twice in my past when I was sick with a bad fever. But I am not feverish nor do I feel sick. Just tired.