Spirits, Or Sleep Paralysis?

Last night while laying in bed I was thinking about the day and what I would be doing tomorrow when I started to fall asleep. I drifted into a light sleep when I started to see my grandma who has passed away about 4 years ago that I have recently been thinking of. She was at my bedroom door standing there, I felt the door opening expecting to feel comforted by my grandmother being with me it felt so real, she was coming towards me and when she got to me I was suddenly awake. I was awake and I could feel it but I could not move my body, open my eyes, or even make a noise.

For a second I thought I was paralyzed this was probably only for about 10 seconds but it felt much longer and was really startling. I remembered a story about this and how spirits can watch you, or was it that it's your own spirit watching down at your body? My mind was completely awake and I was aware of it telling myself to keep breathing and wondering when this would be over? A few moments later I finally moved the tip of my finger and then was able to move my whole my arm, open my eyes and move my entire body.

I was so startled and sat up in my bed, this wasn't the first time I've experienced this but I felt the presence of my grandma but I wonder was that my grandma or something else taking over my body? At first when I saw the spirit of my grandma I welcomed her because I missed her and I thought I might be dreaming after she entered the room and came towards me it didn't feel as comforting and then I was purely terrified by the experience.

Is this because my grandmother was really here visiting me in an unconscious state or was it another entity disguised as a familiar person trying to take over my body or watch me? Or could I have simply been experiencing sleep paralysis?