What causes intermittent pain in lower jaws and between chin / throat?feels like there is pressure under tongue.neck pain.pcp says not cardiac.tmj?

Consult Oral surgeon: You need complete & detailed evaluation including Panoramic x-ray &/or CT scan. Local causes like bad teeth, gum infections, any pathology in soft or hard tissues(Bone) should be ruled out.Any infections even tracking from upper teeth,sinus or even ear, tracking to lymph nodes below the jaw, can be the cause.If this rules out -ve, consult a cardiologist or a neurologist.TMJ check to rule out.

See your dentist: Many different conditions can lead to pain in the floor of the mouth. Your dentist should be able to evaluate your symptoms and to make an exact diagnosis and treatment. TMJ/TMD seems highly unlikely.

Maybe TMJ: Perhaps TMJ. But complicated area anatomically. See an oral surgeon for comprehensive head and neck exam. Once your have a diagnosis, treatment follows.