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