Quantum Apollo 16000 Portable Projector

It sounds as though the unit is overheating. That would explain why the fan keeps running, and once it cools down enough it starts up again. What kind of environment are you running this in? Is there a way to put it in a cooler environment? Even having an external fan blowing on the unit could help.

Honestly, unless you've got it in a very hot environment, it also sounds like a poor design for heat dissipation. Or possibly the heat sensor is bad, and shutting it down at a lower temperature than it should.