Sleep Fainting spell?

Hello! I am 18F I have been diagnosed with POTS for around 5 years, but I have never had something like this happen and I’ve only ever passed out once.

But the other night, I woke up and I couldn’t see anything. My vision was black and I was getting very hot, I honestly thought I had died. When I fully came to my senses, my heart was racing like crazy. It was a little hot in my room but I was hydrated and everything. It was extremely hard to fall back asleep after because I felt disoriented.

Does anyone know what this is and why it happened? I’ve looked a bit online but I can’t find any instances like it. What scared me most was not being able to see.