I am experiencing the same problem, a sharp pain in the left-back of my head that lasts for seconds to maximum a minute.
It occurs randomly, but i don't recall that it happened to me twice a day, sometimes it happens after weeks, months, etc...
I had no accident or any injury in my head, or a trauma
when I went to a neurologist, he didn't know the cause of such a problem, he gave me magnesium pills assuming that i have deficiency in magnesium, but it didn't help
I am afraid that this will get worse later on