Power cycling problem

[NewToTech]

Does anyone have suggestions what the problem could be here? I have just built my nephew a PC for his school work and some light gaming. Used older parts so it’s LGA1155 with the i7 3770 CPU, gigabyte GA-PA65-UD3-B3 motherboard, 8GB DDR3 memory, 600W EVGA PSU, Strix 780, 500GB HDD and 120GB SSD but when I hook it all up to install windows it just power cycles constantly without even giving me the motherboard splash screen, no BIOS screen or anything just power on for a few seconds and then powers off. Obviously most parts are pre owned because of its age but the RAM is fine, cooler is brand new as is the PSU, GPU is fine in my system so I can’t think what it could be at this point. Any suggestions appreciated and I’ll try anything people can suggest and keep you posted on if anything works. Thanks in advance.