Oh No! How very frightening!!!

I imagine there might be a few possible causes.
It's best ot see a doctor if possible.
I hope this never happens to you again!

I am very concerned, especially when you could not summon help.
This might not feel like it's warranted; however, just wanted to share we have these pendants which call emergency numbers whenever we push the button. This may seem like overkill; however, there are times when even having another person in the house is not enough.

I can think of at least several stories where friends have found themselves in unforeseen, life-threatening situations. My neighbors now all have these types of systems, too. People can use them or not, at any given time. I have my mom use one whenever she showers, whenever I am either not home and/or I am on a completely different floor of the house. I also use one if I am home alone, and am not feeling well. Just a thought.

I would like to suggest you sleep with your upper body (and head/ neck) elevated, at least until you understand more about what was/is going on for you. Some people elevate themselves by using pillows, etc, to elevate their upper body. Others sometimes elevate the bed itself by putting something under the legs of the bed (at the head of the bed). I would not take a chance on this happening again.

Please do consult with your physician. This can be very serious, life-threatening.

I am very thankful you are okay!
Please do take good care!