Hi E.,
I'm a mom of 4 (1 boy, 3 girls). It's common for babies to go through these cycles. All of my children were, for the most part, great "sleepers".They'd go to bed and sleep for 11-12 hours straight. But every few months they'd start to wake and cry in the middle of the night (it seemed to happen mostly at 6-7 months of age, 9-10 months,and then then every 4-6 months after that. It would last 3-7 days, typically.
The best explanation I could offer is that these cycles may be caused by what Dr. T. Barry Brazelton refers to as "Touchpoints" in a child's life. Often before a developmental milestone occurs (rolling over, crawling, walking, etc.) there will be a disruption of sorts (crying, waking at night....), as the baby prepares for the next milestone. This explanation certainly seemed to fit with the pattern of my babies' behavior (plus it made me feel better!)
So, once you've ruled out other obvious reasons for the baby waking at night---ear infection, fever, teething, too hot, too cold, etc., you can consider that he's about to experience a developmental burst, and relax. I recommend checking on him, and after you've ruled out the obvious, minimize the time in his room. In other words, a few word of comfort, then a pat on the back and "night-night". I did not offer a bottle or spend a lot of time rocking because I didn't want to reinforce a pattern of wakefulness. I found that after a couple of nights I might hear my baby fuss a bit, but he'd usually be able to soothe himself (or herself)quickly back to sleep.
He will go back to sleeping through the night--mine all did!
Hope this helps, V. S.