I think i have a swollen salivary gland that is recurring periodically over many years. what to do?

Many years problem: You must see a dentist, oral surgeon or otolaryngologist (ear, nose, throat doctor) who will see what your problem exactly is and then determine the appropriate course of treatment.

Salivary gland: Swelling has many causes. In your case something is intermittently blocking the gland's duct. Cause is most probably benign. Next time it swells up get in to see an Oral Surgeon to determine cause and appropriate treatment.