Why do I get nauseous while playing Minecraft?

I used to Minecraft for hours and would be fine, but recently whenever I play for more than 20 minutes I get nauseous and get motion sickness and literally have to exit the room and close my eyes for awhile. It doesn't happen with any other game just Minecraft.

Any idea why?

Added (1). Xbox 360, by the way.

It could be the way the game moves ehen your playing it. Take a break from minecraft. Ps I love the music from that game.