I keep getting lock jaw only on my left side. what should i do?

Open or Closed?: From the sound of its periodicity you should definitely have this evaluated by an oral and maxilofacial surgeon. Ligamentous laxity, internal derangement, eminence slope issues can all be causes.

Be careful!!!: If your jaw is getting 'locked' open or close, you may have TMJ problems that should be evaluated by a dentist asap! try to not open your mouth wide, and the architecture of your jaw joint may begin to 'tighten', but go see a qualified dentist in TMJ disorders, asap ( sorry but i had to repeat it again).

Lock Jaw: This is typically a dislocated TMJ disc that is anteriorly displaced and prevents the TMJ condyle from translating (gliding) forward. You can still rotate the jaw but can't move it forward. The widest movements are limited to about 30-35 mm and then the jaw is blocked. Treatment is to unlock the jaw...We see this often and it is not always reversible. Help is achieved by decompression.

See expert: whether your jaw is locked open or closed, a significant problem. See TMJ expert. Any dentist can be a TMJ expert with the proper training and experience. Most commonly, oral surgeons, prosthodontists, and orofacial pain specialists. Ask your MD, your dentist and your dental society for referrals.