Cutting out all of a sudden

Hello! Yeah my rav4 has been running great! Even today I drove it probably 100 miles in four or five trips. Then all of a sudden after it sat for about an hour, I started it up and it's just cutting out like crazy! It has a half a tank of gas. I have no idea. It was sitting at a park and it's so drastic and all-of-a-sudden that I would almost think that someone tampered with it. But I don't see why or how. Any other ideas? Thanks! George