You'll need to make his lower jaw move, and his neck... well it seems strange the way it inflates and deflates. The shading on the head is not quite the same as on the body, so you'll need to fix that too, because the head looks quite flat.

i'd work more in the smoothness of that idle animation, so it wouldnt look as if the creature was having a heart attack.

Agree with Metaru, right now it realy looks like hes hyperventilating, Its a bit odd. Think more abot the quality of the body. Like, are the muscles of the dragon very flexible and soft?, or are they more hardend so the movment limmited? what kind of skin does it have? is it feathers, scales or other, and how does it react to movment. Becose all these things will affect how it moves. Maybe look at real animals with diffrent skin and how they act and work with there movents.

Also, the loction of the organs, desite what is where. Where is his heart? the lungs? how far do the throat go? becose this will deside what parts of the body will move from the heartbeat and from breathing.
Without this, the hole thing right now feels more like some pulsateing blobb with a dragonhead. :/

But! does look very promessing otherwise, the head is very good (alltho, need more movment), and a good start to the structure of the dragon. keep up the good work.