Computer intermittently won't switch on

[DevPete]

There have been a couple of times where my computer won't switch on. The USB hub lights up when the power is switched on, but when I press the power button, the USB lights go out. It seems to be ok if I switch the power on and off again though.

Any ideas what could cause these symptoms? The power cable doesn't appear to be loose, I had wondered whether it was something like undervoltage protection (my Seasonic PSU has it), or perhaps my surge protector may be having a few issues ? The machine works flawlessly when started (even for gaming).
It's hard to do any diagnoses because it doesn't happen often. The times when it didn't start happened to be colder mornings though, but would have still been at least 18C in the machine.

 

[Plec]

What's your complete spec and age/spec of the Seasonic?

It's a quality branded PSU but power demand, age, bad luck can all be a factor.

If you're plugged into an extension lead you need to rule that out by plugging directly into the wall (bypass surge protector too). And no harm in trying a new kettle lead if you have one.

That said, have you added any new components lately?

Additional - check boot priority in the BIOS. Make sure your main drive has priority.

Perhaps disable fast boot if selected.

 

[DevPete]

The components haven't changed for just over a year and the age of the most components is around 4 years.
Seasonic 750W PX750 (just over 1 year old)
CPU AMD 3950X
AMD Radeon RX7900XT (just over 1 year old)
3 SSD's

I would imagine a good 750W PSU would handle that quite easily. The power light doesn't even come on and the PSU relay doesn't even click, so I can't imagine the GPU would be drawing much power at this point.

The difficulty with trying different components is that I may know if it doesn't fix the problem, but won't know if it does fix the problem because the problem doesn't happen every day.