“Can TMJ go away on its own?”

Yes!!! Most TMJ disorders are initiated by stress. Stress causes you to clench your teeth together causing havoc on your TM joint. Target patients are females in their teens. Exercise and yoga will help tremendously to decrease or stop your clenching. If clenching has become a habit with or without stress can damage your disc inside the joint. Additional dental modalities may be warranted with your license dentist. Other causes of clenching include prescription drugs and obstructive sleep apnea.

It depends on the etiology. A large percentage is myofascial pain (muscular) and that type can. If it is an internal derangement in the joint itself that will not.
I suggest you visit a specialist to determine your particular scenario.