A healthy chicken doesn't usually sleep during the day, especially standing up. It is likely that your hen is sick.
There are many diseases/ailments that would cause the symptoms your hen is describing. I would recommend doing a thorough examination of your hen, checking for any abnormalities on her body. To figure out what is wrong, we need as much information as possible. Does she have any swelling on her body, or any discharge from her nostrils? Any mites or lice? Does she walk normally? And how old is she?
If she is young (less than 4 months), I would suspect Coccidiosis. Coccidiosis is a disease of the digestive tract caused by protozoan parasites. It can be fatal if untreated. Fortunately, it is usually easily treated with Corid (amprolium).
Another possibility, if she's an older hen, is egg binding.