If it's a new bike, bring it back for its 30 day checkup. Most LBSs around here offer that for free on new bikes that they sell. Often the wheels will need to be retensioned. If your LBS doesn't do that as part of the free checkup, or doesn't do that, then pay them the $10 or whatever to do both wheels. Machine built wheels often have low and somewhat uneven tension. Tensioning them right will make them last longer.

There could also be something loose inside the wheel. Mavic rims are known for that. I think it's shards from the rim joining process.