After plugging in, have to wait for 10-15 minutes to turn console on

I got CUH-2116 on my table which acts weird. After plugging in (to power outlet) and pushing power button, it has no effect - console won’t turn on. No sign of life at all - no beep, no cooler whirling sound no HDD, only pushing eject button creates beeping sound. Bu if I wait for 10-15 minutes the power button comes active, acts like it should and I can turn console on. After I’m able to turn it on, it sometimes goes to WLOD mode; sometimes it shows me “Updating firmware” screen followed by “Connect your controller” screen (haven’t had success to get past this yet)…I’m able to turn console off on holding power button and after that power button is “deactivated” again. Just need to repeat the “unplug-plug-wait for 15 minutes” cycle again. Any thoughts how to identify is it faulty PSU or faulty motherboard (APU)?