Michelle,
If you can't see the fan running it is NOT running. And that will cause the temperature inside the case to become so high that the machine turns off to protect the CPU. That fully fits into the diagnosis.
I've had this with a rather high priced rather high quality PC. When I went to the shop with it they set the fan speed in the BIOS to "constantly high" instead of "variable", because somehow variable meant that it wouldn't get enough power to run. Problem solved, although I've got more fan noise now than I prefer. But it's primarily my sons PC and he doesn't mind.
The other possibility is that the fan is just broken and needs to be replaced. Better take it to a repair shop and let them have a look. It's not the most expensive repair you can imagine. Better do it fast. It's not good for the PC to be too hot.
Kees
PS. If ever posting again, think of a more descriptive subject line, like - in this case - "fan not working".
I think the fan is gone on the computer. When I turn the computer on I don't see the fan moving in the back of the computer and today the computer shut off by itself and wouldn't let me turn it back on for about 5 minutes. How can I be sure if this is really a fan issue or not? Thank you.
Michelle

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