My xbox won't play my games anymore, what should i do?

My xbox keeps opening the disc tray on its own repeatedly without me even touching the eject button. And when it finally does close the xbox won't play my games, it acts like there's no disc inside it even though there is. It just stays on the main screen where it says memory, music, xbox live, and settings. By the way this the original xbox, not the xbox 360. If anyone could kindly help me out here, I would greatly appreciate it.