Carbide Spec-Alpha case issues

[midcuk]

Dear All
First time poster so please be gentle. I have a strange issue where the PC will turn on and boot for 30 seconds then turn its self off again, few seconds later it will power its self up then turn off again, it worked fine for a month and then the issue started when i tried to add a second SSD.
So far to try and diagnose the issue i have
1. replaced the PSU (same thing happens)
2. replaced the memory (same thing happens)
3. replaced the motherboard (same thing happens)
4. replaced the SSD (same thing happens)
5. replaced the graphics card (same thing happens)

So basically other than the CPU and the case it is an entirely different PC and yet the issue remains. I have a CPU on order but could it be the case causing the issues ? i can not see how but everything else has been changed ?.

Any thoughts or suggestions would be greatly appreciated, if i replace the CPU and the issue still arises then it must be the case ?

Help :)

Many thanks

Chris