That's exactly how I LD most of the time. I'll be in bed sleeping, and I feel the need to seperate from my "sleeping" self so I can go about my lucid business. It can be quite difficult too, but once i've seperated myself I can go around lucidly and do whatever I want.

I'm sure that happens to alot of people

These types of LDs also tend to be the most vivid and realistic to me.