Yup, it's pretty common and it sucks. My STTN-since-7-week old baby started waking several times a night for almost a month starting right around 9 months. We were spoiled for so long, it nearly killed us. We're finally almost back to normal in the last couple of weeks. For us, he had a bad cold/cough, popped 4 teeth, grew an inch and learned to crawl, cruise and stand in about a 2 week period. I talked to the pedi about it and he said there can often be a sleep regression during this period because they're learning so many new skills and becoming even more aware of their surroundings, making it hard to sleep with all that brain activity!
Could your son also be hungry for some of those night wakings? My son hasn't eaten at night since 7/8 weeks and during that really intense 2 week period, he woke up a few nights in a row just ravenous, taking in close to 14 ounces of formula each night. A few days later, he was an inch taller so he was eating to fuel the growth spurt!