SoNanny My daughter started doing this at about that age. She had just recovered from a cold, and had received a lot of attention when she woke snuffling in the night, so she kept it up when she was better. I was 8 1/2 months pregnant at the time and just could not face it, and my husband was working long hours and needed his sleep.
I took her to the GP, who gave me a week's supply of antihistamines for her. This made her sleep well enough not to wake so easily, and when I stopped them at the end of the week, she was out of the habit. Thank God I did not have her waking at nights as well as a new baby.
They do not approve of antihistamines these days for young children, but I'm sure there is an alternative. They just need to break the cycle and get him back into the habit of sleeping.