There should be a code on the MOBO where the manufacturer support of the motherboard can help, or google what this code means. This is how you can isolate the error if the BIOS does not start. I also had such a problem, which I solved with the support after several attempts: the CPU cooling was screwed on too tight, solved one turn and finally continued. With a self-built PC for around 1650 euros, that was very stressful.