Can a computer work without OS 1

Even an assembled PC without an operating system does not start the BIOS

Hello everybody,

I urgently need the help of the widely acclaimed Computer Base Community. My problem looks like this:
I put together all the parts for a gaming PC on Mindfactory and ordered them. At first I wanted to have the components assembled, but I figured I would save money and learn something if I did it myself. So I was busy building such a PC and tried it, but now the thing is completely assembled and somehow doesn't work. I mean that the fans are running, the buttons on the case work, the LEDs light up and everything else has power because I checked the cabling again, but the BIOS does not start when I switch it on, although I do as described in the manual Pressed F2 or Remove. Actually, the BIOS or in this case the UEFI should start after all, even if no operating system has been installed, right?

Here are the built-in parts:

Intel Xeon E3-1231v3 4x 3.40GHz So.1150 BOX
ASRock Fatal1ty H97 Performance Intel H97 So.1150 Dual Channel DDR3 ATX Retail
16GB Crucial Ballistix Sport DDR3-1600 DIMM CL9 Dual Kit
Thermalright HR-02 Macho Rev.B tower cooler
LG Electronics GH24NS DVD-RW SATA internal black bulk
1000GB Seagate Desktop HDD ST1000DM003 64MB 3.5 "(8.9cm) SATA 6Gb / s
SanDisk Ultra II SDSSDHII-240G-G25 240GB internal SSD (6.4 cm (2.5 inch), SATA) black (not yet installed, will be delivered)
4096MB Gigabyte GeForce GTX 970 Windforce 3X OC Active PCIe 3.0 x16 (Retail)
500 watts be quiet! Straight Power 10 Non-Modular 80+ Gold
CoolerMaster K282 Midi Tower without power supply black

I would be very happy if you could help me further.

Greetings MisterToastbrot