At this age I don't think the LOs have complete control on how they move their arms and hands quite yet. S has done this before several times. Tugging the hair might be soothing for your LO.
V is an occasional ear tugger- she expresses no other symptoms of having an infection but I am still going to have them checked out at her 6month checkup next week. Her ears do stick out quite a bit right now and she is a VERY grabby handsy baby so I think she just likes to get a hold of the first thing she can which happens to be her ears. @deecee9580 it could be a similar situation where she enjoys the sensation but ask the pedi at her next checkup.
Re: little one hits herself in the head!