The book mentioned in previous posts: http://www.uesp.net/wiki/Skyrim:Amongst_the_Draugr.
They do seem to be conscious undead:
...the only utterances they make seem to be in that heathen tongue that I can't even pronounce... I learned more of their intentions towards me from their general movements and tones rather than specific words.
They don't just "sleep until disturbed". It's apparently just coincidence that they're (usually?) all dormant when the player finds them:
Every day, a different set of draugr would awaken, shamble their way to the sarcophagus of their priest, and prostrate themselves before it. Several hours of this, followed by a meticulous cleaning of the area. It would appear that the adherents of the dragon priest continue their worship of him in death, which would also explain the ferocity with which they defend his chambers.
From the text as a whole, it is apparent that nobody tends the draugr for it is the draugr themselves who tend the dragon priests. The torches and candles are presumably for their own use; as far as I am aware, it hasn't been stated that draugr have any form of night vision, so they would need light sources to avoid accidents while making their way to and from the dragon priest's chamber.