Has the dog been fixed. Common problem They have medication to take care of that. My lab takes one pill everyday and another once a week.
This was my fist thought. My lab does it every now and then. Maybe 2-3 times a year, max. I've seen her do it while sleeping right next to me. It woke her up and she went running thinking she'd get punished. Can't really get mad at her for it.
Plus, I'm partially to blame. It's an easily medicated issue, as everyone has been saying, but I'm not the biggest fan of medicating for a non-serious/constant issue. That's just me, though, and can perfectly understand others that do.