I have two very different children. My son, my oldest worried me when he was a baby/toddler. I thought he may have mild autism. He showed a few signs but, IMO..most children show some signs, doesnt mean they have Autism...but it is worrisom. My son had sensory issues and is a little quirky. He is now 8, doing very well in school but still has mild sensory, and a few quirks.
You are doing the right thing. Bring it up with his doctor. Most likely they will say..he is fine and will grow out of "it". IF when you leave the office, and are not happy, or relieved with what the doctor says...go with your gut! For ME...when I am unsure about anything with my kids, I have it checked out until I am satisfied. I helps me not worry as much, and I know for sure.
I think you son could use therapy from what you posted. OT...for his sensory, and he may be abit delayed in speech. My son had both, it made me feel better, it helped him, and helped me know what I needed to be doing on a daily basis for him to overcome his issues.
My son didn't have clothing issues, but he did flap(a huge sign) he needed to jump and throw things, when he got excited, he got so hyper and was hard to calm him, which was all because of his sensory issues. I would say your son has sensory issues, but different(opposite) than my son. I was told my sons body "needed" the information it got from flapping, jumping and throwing. Your sons body may need to rock to get the info it needs, and doesnt like the way his socks feel, or he has OCD..the blanket/sock thing. playing with his hair may be the way he found that calms him. (does he do it to calm himself, when falling asleep, while watching tv? My son had a lovey and a pacifier, which I allowed him to keep for to long, I felt he needed it...and he did.