Weird problem with my pc

[s.i.m.o.n]

So after building my pc I had some difficulties getting started. It all went fine when I had the solution to the problem and had no issues since.  Just a few minutes ago I returned home and wanted to turn on my pc. As always I had shut down everything before leaving (with the on off switich on the back off of my case off). Turned that on and then wanted to turn on my pc by pressing the on button (I knew that I had power because the rgb on my mainboard lwas lit) but instead off powering everything on it just turned everything off (lights out on mainboard etc). I was able to reproduce the same weird thing another time (same procedure to turn my pc on). After that i never had the issue again. I would be really thankfull if someone knows what the issue could be or if this is normal or something im kinda freaking out rn so yeah...

 

My specs if that helps:

i7-9700k

Asus GTX1070 strix

Asus Z390

2x8gb HyperX

Samsung ssd 970evo

Western digital SN500

Be quiet! Dark Base pro 900 rev.2

Dark Power 11 600w

Thermaltake Water 3.0 360 rgb