Might be nothing much (overexcited “playing”, etc) might also be a lot else:

• senility
• dermatological reasons (allergies, parasites etc)
• mental health (OCDs, just like with us)
• extreme boredom and lack of sensoric diversity etc.

Surely hard to diagnose with a 2seconds-gif. If that occurs once a week and seems harmless (no wounds, blood, hairloss) it probably is.