Bantam Hen Problem - Help Urgently Required

Having just been up to check my chickens ne of my bantam hens was sat in the corner not moving whilst all my other chickens were outside running round.  We took her out of their house to find her alive and breathing with her eyelids closed and not responding to anything.  Almost as if she is unconscious.  We have brought her inside the house and since being inside she seems to be moving her neck slightly but still her eyelids are shut.

I have not noticed her acting any differently over the past couple of days and she is only two years old.

Can anyone suggest what this could be?

Thank you for the fast response.  Having done a bit more research on egg bound chickens this might be the cause.  Currently keeping her warm to try and relax her and she seems to be breathing more visibly and has opened her eyes a few times so seems to be perking up.

See thing is having checked her over she doesnt look like she has an egg inside her.  She does however feel rather cold.  We shall keep an eye on her and I shall let you know how she gets on.

Thank you for the advice.  We have put an electric blanket wrapped in a towel on a low heat setting under her.  Should hopefully perk up over the coming hours...

oh so sorry  , not sure what to say but lots of hugs xxx

I'm so sorry