It sounds like a form of sensory seeking, in which case the best options are to either let him continue or redirect him by offering a sensory aid that provides similar sensory input. I think some types of fabric (possibly silk or felt) could provide similar tactile input; you could attach them to pieces of something like cardboard or wood to turn them into portable fidget items.

My son's OT recommended a chew necklace & bangle (it looks like a hard rubber dog tag), as my guy when anxious would twist his lip or lick. These are specifically for kids with ASD, & it helped. Certainly cut down on us getting sick from picking up germs he'd been touching. I put them through the dishwasher at night.

My little guy likes to rub heads he even likes to rub my head or face on his belly

Thanks for all of your answers and suggestions.