OptiPlex 7080 Tower

I have an Optiplex 7080 Tower that I am stumped with, it just shuts off randomly and will not power back on for the user. I can go down and unplug the power and power it back on, then will run for a short period of time and then do the same thing. I have run all of the diagnostic tests and everything passes. I have done all of the driver updates and still having an issue. My next step is to replace the power supply but wondering if I might be just chasing a dead end issue. Perhaps just replacing the unit is a better solution.