Welcome to the forums my friend!
- What exact PSU make and model did you have before and what make and model did you replace it with?
- Are your RAM modules from the exact same pack? (not just the same model)
- Have you tried removing GPU and running on integrated?
- Do you have a MB speaker to listen for any beep codes?
- Did you change anything before the issue started occuring?
Was Corsair hx850 went with hx750 due to price,same ram modules,tried without gpu same thing,no beeps from Mobo,it literally starts for a second,kicks the fans in and then cuts off and repeats,and I haven't touched the PC since I built it 5 years ago.