You should list a few of the things you have tried at least, also the motherboard model CPU, a picture of the screen could be very useful.
Something that could happen is that your pc is stuck trying to recognize, either your HDD or the RAM,and its having issues, first I would recommend to unplug all your drives, if this doesn't work, leave only one memory on the slot, switch it from slot to slot, and test in between, If you have many sticks, try the same with the others, all this until you get it to the bios or try to boot .