Your dog could have any number of problems; See a Veterinarian.
Because it's got rabies! Just kidding! It's probably because they are not outside too often, so they are not sociable, they sometimes do it to catch your attention. Or that's they're personality.
It keeps on scratching itself.
I think its got hurt and ate something bad.
cartlilage !
Cone collars seem to work well. They go around the dogs neck, such as a normal collar, but they have a large plastic cone that blocks the dog from licking, biting on its body, or scratching at its head.
sounds like ear mites
Odds are it has something to do with the disc scratching. Make sure the console is flat and not vertical, along with the disc being clean.
You may want to consult a vet to thoroughly check for fleas or ticks. Although scratching or biting is perfectly normal for dogs, obsessive biting could mean there is a more serious problem. check the spot where your dog keeps biting, and make sure there is no irritation or (tick, fleas, ect.). If you give your dog many baths it may just dry skin, try bathing less often or use a moisturising shampoo.
Well time to visit your doctor.
It is the pick guard. It keeps your pick from scratching the guitar's surface.
If your 5-month-old keeps biting his lower lip, you can try giving him a teething toy or a cold washcloth to chew on. This can help soothe his gums and reduce the urge to bite his lip. You can also gently redirect his attention to a different activity when you notice him biting his lip. If the biting persists or causes any discomfort, it's a good idea to consult with your pediatrician for further advice.
If it is a female, she could be going into season.