Nausea after eating..?

Sometimes after eating, I get nauseous. This usually lasts 15-20 minutes, then I'm ok after that. I never throw up or have any other problem. And it doesn't seem to matter what it is I'm eating...low fat, high fat, low carb, high carb, doesn't seem to matter. Sometimes it can be something I just ate yesterday that sat just fine, and the next time, it makes me nauseous. Anyone have this, or any idea what is causing it?