Hm. Let me ask you if he met his milestones in development on time? Does he communicate in other ways with you, gesturing and pointing? I'm not sure what is going on, but I do think you keep your eye on this. You've raised other children--- so you know what to expect. Not every child is the same, of course. But you have a general idea. If these things continue, a developmental pediatrician or occupational therapist may be ideal for an evaluation.
My son has sensory integration disorder which is a delay of the nervous system. He was constant motion as well. His nervous system craved intense play, crashing, running, etc. He was always on a mission to get this input. Now we give it to him in appropriate ways, and he can remain calm when he needs to. He was 3 when we first had him evaluated and it was inconclusive and so we re evaluated at 4. By then it was clear. The licking is a seeking activity.
I don't say this because your son has a delay of some sort, I don't know. But my son is very smart, met his milestones on time or early, etc. But something was a little off. We got the right diagnosis for it and our boy is doing fantastic now at 6.
So, just moniter this closely. If his speech still lags behind, a speech eval would be good too. good luck
I should also mention that from the time he wakes up till the time he goes to sleep he does not sit still AT ALL always running, jumping, climbing, falling all day everyday but it seems to be the same everyday in the same order over and over again even if i try and change it with games we have to play the same game or do the same thing for about 20 min .... he still does not sleep all night he will wake call me and then go back to sleep about 3 time a night and he knows as soon as im not in the room cause he starts screaming if i leave to go bathroom. Sorry it is very long but his ped only tells me he is overstimulated and wont listen to my other concerns.. i have another appointment with him next week..