Assuming it is overheating, and before spending money on an external device, see if the tips Microsoft provides about placement of your Xbox help:
- Put the console in an open area with lots of ventilation. Do not put the console in an enclosed space.
- Do not stack other electronic devices on top of, underneath, or against the sides of your console.
- Make sure the console and its power supply are on a hard, steady surface. Do not put the console on anything soft (such as a bed, sofa, or rug).
- Position the console away from heat sources, such as ventilation openings on televisions and electronic devices. Also, keep the console away from heating vents and direct sunlight.
- Position the console away from high-vibrating sources, such as low frequency speakers, subwoofers, etc.
And whatever you do, absolutely do not place your Xbox next to a picture of Clippy:
