Maybe you're changing your breathing pattern (it has to remain like it is when you're sleeping), or you're becoming too excited. The energy you're feeling is probably SP or the beginning of a dream.

It helps if you imagine the dream you just came out of, including imagining tactile, auditory, and visual sensations. If you were walking along the sidewalk, imagine the feeling of your feet moving along the concrete, and imagine the sounds around you. Daydreaming helps you trick your mind into thinking you're still asleep... until you get into the real dream, that is.