What could be a reason a server shuts down after a few minutes of being powered on?

A server shutting down shortly after being powered on is often indicative of CPU overheating. When a server's CPU temperature exceeds its operational limits, it triggers thermal protection mechanisms to prevent permanent damage. This can happen due to inadequate cooling, such as a malfunctioning fan, dust clogging vents, or improperly seated heat sinks. Once the CPU overheats, the server will power off to protect the hardware from damage.

In the context of the other options, while a redundant power supply failure could lead to instability, it wouldn't specifically cause a shutdown after a few minutes of operation. Memory failure may cause a server to crash or fail during boot, but this typically wouldn’t result in an immediate shutdown after power on. Lastly, hard disk failure, while detrimental to server function, usually does not cause the entire server to shut down, as the server can still operate without the hard drive for a limited time, often allowing access to system BIOS or other diagnostics.