Question My PC starts for a split second and shuts off again

Oct 18, 2018
So today I was playing GTA fine, I left for driving lessons and switched my pc off by the power supply switch at the back. When I got home I hit the on button and it started for a split second and then stopped, nothing appeared to have any power but I wasn’t sure, I dismantled the PC and rebuilt it and the same problem occurred, I’m not quite sure what’s wrong with it and I need help. I built this rig in December last year and haven’t seen any problems until now.
CPU - Ryzen 5 2600x
MB - B450 Tomahawk
RAM - 16GB 3200Mhz Corsair vengeance lpx
PSU - 550w Corsair V something
GPU - 1050ti
Storage - 2tb WD blue and Kingston 120GB SSD