Without seeing him, I would have no precise idea. I can only guess, in truth.
First, watch his eyes. What he is looking at interests him, unless he is looking inward for some reason. If he is, he may well be fearful (again, a guess). The desire for security is often
motivated by fear, and the desire for 'contact' involves reassurance. I would look, watch,
and listen before I did anything regarding censure (unless the child was doing something
dangerous to himself and others).
Secondly, (I'm thinking carefully. I do want to help) such behavior may well be transitory - or, it might not. I've enjoyed being rubbed as far back as I recall (roughly two or three years old). The stimulation imparted by certain types of contact - say, back rubs - almost puts me in another
world. To be touched says 'you are my friend'.
I hope this is of some help,
D. Y.