Sporadic vomiting

Q: Our puppy is currently 5 months old. She seems prone to vomiting. In some cases, it's obvious it's due to her eating organic matter outside that she shouldn't. For others, it's unclear what's causing it. She tends to vomit at least once every couple of weeks. Almost 99% of the time, she will vomit only in the middle of the night. The color is usually yellow/green. She still maintains her usual energy level, appetite, and consistent potty schedule. The vet also didn't not detect anything obviously wrong with her in her recent appointment. What could be causing this?

A: Vomiting that infrequently is common. You may not figure it out but I would try starting a log of what time, how much and what she eats and see if you can spot any pattern.