What specialist should I see to treat tmj?

Dentist. Start with your dentist, you may need an orthodontist.
Depends. Contact your dental society for names of regional TMJ "experts". It may be a prosthodonitst, oral surgeon, or orofacial pain specialist.
TMJ/TMD specialist. I would ask my dentist to refer you to a tmj/tmd specialist. Some regular dentists do treat tmj, but i would ask them to refer you to a dentist who treats tmj. If in doubt, oral surgeon, neurologists and ENT offices are great for knowing who to refer to.
No specialty exists. Start with a general dentist that really understands bites and tmj. Currently, there is no recognized specialty, although many doctors focus their practices in this area.