Will a dislocated jaw reset itself?

Yes and No: If it is very minor most can reset a dislocated jaw, but a more severe dislocated jaw usually needs treatment from a doctor. I posit if you have a severe dislocated jaw the pain will dictate you to the doctor to have it treated.

Sometimes: It is possible if the dislocation is not too severe. Otherwise u will need to seek treatment.

Unless by trauma ?: If due to trauma it is understandable but if it just occurred, for known reason, i would be seeing my dentist to have my jaw checked.

Sometimes: Sometimes. Usually better not to take a chance. See oral surgeon ASAP.