Sound Asleep

I don't know if anyone else experiences this phenomena.

Most night I sleep fairly well. I wake up rested well enough to go about my activities for the day and I don't feel too terribly groggy or like I am dragging my feet. Sometimes I feel a bit tired, and some days I feel like I have a little extra energy. I figure it is about the same with most other folks that I know.

However, on occasion I have a night where I absolutely am dead to the world. Last night was one of those nights. I'm talking about the kind of sleep that is so intense you never move and when your alarm goes off in the morning it feels like your limbs are full of cement and you can't move them. Sleep so intense that when you sit up for the first time you have to wait a minute before you get up because you aren't sure you are really awake.

The strange thing about this is it never happens after I've been exhausting myself with physical activity, or when I'm sick. It just happens on random occasions, not very often, and sort of comes out of the blue. I can't come up with an explanation for it, but I feel so awake the day after I sleep like that I wish I could do it every night.