It sounds like he is jolting himself awake which is totally normal. It's also normal for new borns to sleep lightly and wake a lot, it's actually safer for them not to sleep so deeply. The things which got babies to sleep more deeply, methods used by previous generations are considered higher risk factors now. Are you able to set up his cot by your bed so that you can sleep with a hand on him? I used to do that with my DS, he was in a baby hammock by my bed andI could lay a hand on him so he felt close but was in his own bed learning to sleep there.