I get random headaches in the left/rear region of my head several times a day in one week bursts; not triggered by light, sound, sleep. What are they?

Headache diary. It sounds like a headache diary might be a good idea for you. Start keeping a log of the times you get your headaches, the type, location and severity of the pain and what was happening right before it started. This should include what you're doing, eating, any medications you're taking, etc. Taking this critical piece of history in to your doctor should be a great help in figuring this out.
Migraine headache. It can be migraine headache, usually migraine is triggered by stress either physical or emotional, the classic migraine usually is proceeded by an aura as warning symptoms and are mostly visual disturbance the a unilateral throbing headache will follow and that is associated with n/v and/or photophobia/ phonophonia. The common migraine is in both sides and without an aura.
Many Causes. There are many causes of headaches including inflammation, vascular, blood pressure, dental, eye, depression, thyroid, etc. However, most people have primary type of headaches: migraine, tension or cluster. See the attached photo. The international headache society list all criteria http://ihs-classification.Org/en/02_klassifikation/.
May be Cluster. Sounds like it might also be cluster headache. The treatment is similar to migraine but can sometimes be stopped by oxygen inhalation.The preventive meds are approached a little differently than migraine so if the treatment for migraine doesn't seem to work, you might consider cluster treatment.
Chronic headaches. This may be migraine or cluster headaches or something else. You need to call your doctor for an examination to determine the cause.