Hmm, I sort of understand... and sort of have a similar issue myself. At my workplace, the kind of work I have to do leaves me sitting at a desk for hours upon hours doing absolutely nothing, but I have to be available in case something ever comes in. So I usually just stare at my desk, and when I do, I find myself slipping into a dream-state you describe. But for me, it is more of a nightmare-daydream. When my mind aimlessly wanders I tend to think about bad things happening, or just feelings of depression. I don't know what you can do... but I'm right there with you.