The click is just the relay switch on the RM750x power supply as it turns off. That's normal. The real question is why is the computer restarting.
- Look at your surge protector, is it old and causing the problem? If so get a new one with a light so you can ensure it's working correctly.
- Is the power cord plugged into the surge protector all the way and seated firmly in the back of the computer or does it wiggle, as in it's loose? If it's loose in the back of the computer when plugged all the way in, then get a new power cord that plugs in firmly.
- Do you have a lot of stuff plugged into the wall socket or surge protector the computer's running on. I've seen people plug half their house into the wall socket they're running their computer on and flip breakers. Try to use just your computer into a surge protector on a single wall socket.
If that's all resolved, then the 750 watt power supply should not be overheating with that build. That's plenty of power supply for that build. So it's something else... Hmm...