Is my gerbil dying? He's cold and won't open his eyes.?

I have a gerbil (3 yrs.) and today I went to go check up on him and he is in his little house and his eyes are closed and I pet his and he's pretty cold I gave him a little piece of carrot and he ate it. He usually bites me and attacks me when I put my hand in the cage but he's too weak to try. I was watching him for a few mins and he occasionally shifts his position but never opens his eyes. Yesterday he was completely fine. Now he won't open his eyes or get up he just mostly sleeps. I don't know if I should pick him up to try to warm him up or leave him be I put some bedding in his little house but he's still cold what do I do please help!