When we sleep our bodies are suppose to go into protective mode and basically become paralyzed so we don't hurt ourselves. It sounds like you may have a sleep disorder and since you are actually getting out of bed while still not awake I would suggest you ask your GP for a sleep study. I've had one for sleep apnea and it wasn't difficult.
You typically spend the night in a comfortable room (not usually a hospital). They put sensors on your head to monitor your brain waves and check when and for how long you hit each sleep cycle. You also have sensors on your arms and legs to monitor your muscle movements. They monitor your breathing and heart rate. And there is a camera in the room to watch you for any activity.
Its very easy and you get your results within a few days. Once they have the results they can treat it.
Good Luck.