I have those symptoms. As I drift off to sleep I’ll hear all sorts of noises that wake me up. The most common one sounds like something heavy moving across the floor. I wake up and immediately know it was in my brain. My body sometimes will do a quick spastic shake, also as I’m drifting off to sleep.
For me it is a loud click like someone throwing a switch. I always thought it was coming from my CRT TV. It still happened when I got a flat screen and I happened to stumble upon an article about sleep disorders.