Sri Aurobindo
Letters of Sri Aurobindo
Volume III - Part 4
It [walking around as if in a dream] is a very usual experience. It means that for a moment you were no longer in your body, but somehow either above or outside the body consciousness. 
This sometimes happens by the vital being rising up above the head or, more rarely, by its projecting itself into its own sheath (part of the subtle body) out of the physical attachment. But it also comes by a sudden even if momentary liberation from the identification with the body consciousness, and this liberation may become frequent and prolonged or permanent. The body is felt as something separate or some small circumstance in the consciousness or as something one carries about with one etc. etc.; the exact experience varies. Many sadhaks here have had it. When one is accustomed, the strangeness of it (dreamland etc.) disappears.