Heat n Glo fireplace turning off and on

[Engineer99]

I have a Heat n Glo gas fireplace. It’s likely a 2001 model. It has a simple on/off switch and a pilot that stays on continuously. When we turn the switch to on, the fireplace lights for a few minutes and then shuts off, but the pilot stays lit. If you leave the switch in the “on” position it will continuously relight itself and shut off. 
What could be the issue?

Edited February 15, 2020 by Engineer99
Fixed subject

[Dave K.]

I recommend starting with the model number and the following link to the manufacture: https://www.heatnglo.com/owner-resources/troubleshooting-and-faqs.  The site also have instruction manuals, installation guides, and parts lists specific to you model. 

[Jim Katen]

Is this a ventless model?