Why doesn't my computer start up the first time?

Question

Computers

Good afternoon. Lately I've been having trouble starting my PC. After updating the components with a new processor, video card, power supply, there was a problem with starting. The PC starts up 3-4 times. That is, the first time you press the power button, the PC turns on for a few seconds, then without pressing anything, it starts itself, but without starting the HDD. After that, I hold down the power button, turn it off and from the next turn on everything works fine. When the PC is already turned on, it works stably without failures. What could be the problem here?
If needed:
To before upgrade: PC after upgrade:
Intel Pentium 2.40 Ghz --> Intel core i3-2120 3.30 Ghz
Intel HD Graphics --> Nvidia GeForce GTX 650 Ti
200 W power unit --> 500 W power unit
RAM: 8 GB

Answer 1

point to the sky - by any chance, in those cases when the computer does not turn on, was it turned off by the button on the case or the 'menu - shutdown', but otherwise it is not buggy?
One of the reasons for the strangeness with on / off is problems with acpi, with power management. With a high probability, they are repaired by updating the BIOS and updating the drivers for the motherboard from the manufacturer.

Answer 2

Sounds like a problem with the power supply. I would look in this direction. Sometimes this happens when the capacitors are swollen.

Answer 3

Update bios
And the case does not fight with static?