Baby is sleeping too much. So much?

My baby is only 8 days age. He is sleeping a lot. Sometimes it is very challenging to wake him up for feeding. He is on demand breast feeding. But due to his sleepiness he hardly demands for food. So we wake him up after 3 hours and try for feeding. Then also he is taking for only 10 12 minutes and again sleeping. However, when he wakes up he continuously moving hand and legs. His birth weight was 3.360 kg. But now he is 3.1 kg. He had slightly elevated bilirubin level before discharge i.e. 9.6. Rest all the parameters like tsh, g6pd is under normal range. My question is is this normal to sleep so much? What should i do if it is hard to wake up for feeding. How to regain his weight. Is there any chance of SIDS as he is sleeping so much? We are very much worried. Please help