The computer powers on only after the second or third try
The mostly likely problem is that the power_ok (or power_good) signal is sent before the power supply has stabilised. Get a better quality PSU. In modern PCs, the power switch is a logic device that tells the PSU to supply full power to the motherboard. The power_ok signal tells the motherboard that the power supply is available and stable. If the signal is sent too soon the motherboard does not recognize it and stays off to protect itself. This can happen in lowerquality PSUs. Booting more than once is not recommended, and you will be better off getting a better PSU.