B450M sometimes won't power up

Hi,

I have the weird problem that my PC sometimes just plays dead when pushing the power button.

This can happen when trying to turn it on after a normal shut down or even when PC just went into standby.
Pushing the power button just does nothing.
Turning PSU off an on again let's turns the RGB LED of the mainboard on, but still no reaction when pushing the power button.

I tried:
BIOS Update
CMOS reset
Replacing CPU
Replacing RAM
Replacing GPU

Nothing worked, problem remains.

Only thing that works is to turn off PSU for about 10 minutes. Then systems starts normal.

This happens like one or two times a week. Rest of the time PC works like a charm.

Any idea what that can be?

System:
B450M Steel Legend P4.60
Ryzen 5 3600
GeForce GTX 1060
RAM DDR4-2400

Cheers
Gordon

I'm having the EXACT SAME issue!

B450m Steel Legend P2.10
Ryzen 5 3400G
XPG Spectrix D50 8GBx2 2666Mhz in slots A1 B1
XPG 480GB M.2 NVMe
TP-Link dual band PCIe Wifi adapter
Corsair 80+ Bronze VS450
x2 12cm Chassis Fan
No discrete GPU

I used to have a 4GB RX370 but after some time it gave me some problems and i discarded it. Many times the PC wont boot unless i power on without the GPU. The GPU is likely to be problematic and has never been used since. Then i bought a new set of RAM which are the ones mentioned above, replacing my HyperX 8GBx2 individual RAMs (not a kit like the XPG). At first, they work brilliantly. After sometimes they started giving boot issues. I tried with so many different slot combinations and eventually figured that the PC runs fine with only 1 RAM stick in slot B2. After a year or two running the PC like this, it got updated to Windows 11 without my consent. So i thought maybe this time i can retry the dormant RAM. Now they are running with the current configuration as above. But even before fixing the dormant RAM, this PC has had a lot of trouble powering on. From refusing to boot to Windows, now it simply refuses to power on. It had some boot loop issues before. Like when i power on the PC, it powers on, but nothing comes on the display. then it powers itself back off, then powers back on by itself for almost infinity. it usually stops doing that and boots like normal when i re-seat or change the RAM position.

Also, sometimes when i accidentally nudge my PC table, the PC will abruptly hang/freeze and the display will go blank. I have to force shut down and restart. After a while, that problem seems to have resolved somehow but i dont know how. I do still quite frequently nudge my table today but fortunately the PC still works as usual. The more frustrating problem now is that sometimes after shutting down, the PC wont power on again even sometimes after waiting for just 5 minutes. Sometimes, it will fail to boot during a restart and then refuses to power on after i have to force shut down. sometimes it wont wake up from sleep. I'll set it to sleep then when i press the power on button, it wont respond. it wont respond to anything even mouse and keyboard. i have tried all those methods above mentioned by the previous user and also tried "shorting" the power pins on the board and still the PC wont turn on. so this means that everytime i shut down the PC, or lose power, i wont be able to turn it on for at least 30 minutes to an hour or more. this is extremely unreliable.

do i really need to suspect the PSU? i have played games with this PC before and i have to say i havent experience anything funny when the PC is running in whatever loads.