In certain parts of my head I feel like a tense feeling for a few seconds and then it goes away. What could it be?

Brief twinges. Brief twinges, spasms, shooting pains, or other aches lasting a few seconds about the head and neck are almost always the result of a nerve getting too much pressure from the spine, usually in the context of arthritis or previous injury. Most discomforts lasting only a few seconds represent pressure on nerves, since almost all other pains tend to last significantly longer.