Custom built pc will sometimes turn on

So, I built my custom pc about a month and a half ago and it worked perfectly. About a week or so ago, it stopped turning on consistently. I always get an led light from my headphones (which turn on whenever there is electricity flowing through the PC, but the fans, motherboard, etc. don't boot up. Sometimes I turn it off and on again about six or seven times (sometimes more) and switch the outlet and it will eventually work again. Then next time I want to turn it on, I hafta repeat the same process.

Does anybody have any clue what the problem might be?

Thanks in advance

Here are the specs:

CPU: Intel Core i5-4670K 3.4GHz Quad-Core Processor
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler
Motherboard: ASRock Z97 EXTREME4 ATX LGA1150 Motherboard
Memory: G.Skill Ripjaws Series 8GB (2 x 4GB) DDR3-1600 Memory
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive
Video Card: Gigabyte GeForce GTX 770 2GB WINDFORCE Video Card
Case: Corsair 200R ATX Mid Tower Case
Power Supply: Antec High Current Gamer 620W 80+ Bronze Certified Semi-Modular ATX Power Supply