What Causes Excessive Sleeping, Lack Of Appetite In Elderly Person?

I have an elderly parent who for some reason has been going through bouts of lots of sleeping, very little eating or drinking. This is the second time in 2 weeks we are going through this issue. We started yesterday with only eating a bowl of jello and drinking a cup of tea and not very ambulatory without lots of help. Today we have had six crackers, a cup of tea, half a bowl of ice cream and still not ambulatory and almost fell down when trying to get up to go to the bathroom by himself. I am wondering if it would be a good idea to take him the ER.