It sounds like sleep paralysis. I suffer from it too. I had some very bad episodes a number of years ago, and of course it is very terrifying when you don't know what it is. The panic that arises from being unable to move, hallucinating and fear of impending death etc is scary, but once you know that it is completely harmless and not some supernatural occurrence, it becomes manageable.
I found sleeping on my back was a trigger, so try to avoid it if you can. Sleep on your side and place thick pillows in front and behind you to stop you from rolling over. Or if your bed is next to a wall, sleep as close to the wall as possible. Over time you will train your body to not roll on to your back.
A lot of stress triggers it too, and my worst episodes were when I was under a lot of stress and very depressed etc. Are you currently under stressful circumstances?
Now that you know what it is, the next time you experience it, it will be scary initially, but you can just distract your mind by chanting to yourself something soothing like "this is not real, it is all in my mind, it will pass soon" etc. Also, the instinct is to focus on the hallucinations and unpleasant sensations, but try to force your brain to wiggle your fingers or toes. That helped me "trigger" my body back into movement and the paralysis faded away.
I haven't experienced it for a few years now, even though I have started sleeping on my back again. Hopefully it will be a passing phase for you too