Weird thing is when I slightly tug the front header wires, the pc will light up and fans for a second then power off again.
Verify that the front panel connections are correct. If you have something connected wrong it wont respond to a push button soft start. But something is definitely funky with tugging header wires and it reacting like that. Maybe the case is messed up where the wires are pinched to ground or something.
One test to try is disconnect the RESET and POWER SWITCH connections and cross the 2 pins for POWER SWITCH and see if it will boot. It should only require crossing the 2 pins momentarily with a screw driver and not touching other neighboring pins when doing this to start it. If it starts then its a front panel wiring issue. If it doesn't start then the main board is messed up somehow.
Lastly if you forget to connect the 12V molex header for CPU power you can actually get a condition where the system will 1 second boot and shut down, so be sure that the CPU power molex is connected for the 12V for CPU power.
