4 beeps then 1 short beep

Hello All, I've got a Gigabyte B360M DS3H Mboard, I've just built a new system with it. However, it won't post... I get 4 beeps then 1 short beep, although the PC reboots during the short beep so for all I know it could be a long beep? :) I've tried googling but can find a matching result...