I've often noticed (and I'm probably not the only one to do so) that when I wake up in the mornings I am reluctant to leave the comfort and warmth of my bed. The instant I make any move to leave my bed (such as throwing off the covers) I have no trouble and can immediately go about my day but if I do not I will lay there for a while.

Is this in any way adaptive? It seems to me that staying in bed would be counter-productive. In ancient times this would surely mean missing out on the opportunity to spend more time hunting or foraging and therefore having a more secure future

Any thoughts as to why we do this?

I work in and underground mine here in Australia.  One of my co-workers sneezes whenever he drives out of the entrance to the mine.  Shortly after we travel from the darkness of the underground mine and into bright sunlight.  He's been here for 22 years and says that it happens every time.  Why?