BINGO! Especially on a fairly new bike. Look for holes on the inside circumference of the inner tube. The tiniest little crescent of exposed spoke hole will do this.

Other common possibilities:
1. Riding with too little air pressure will produce flattened tubes that look like a snake bit them.
2. Using a pump with no hose too carelessly. Look for tears at the base of the valve stem.
3. It's possible to have a piece of glass or wire imbedded in your tire. If you always line up the tire's trademark with the valve stem, the hole will be in the same place on the inner tube.