I have a weird start-up issue on a pc I acquired and am now using as my main desktop. It has an Asus motherboard and UEFI 'BIOS'. Everything seems to work fine. There are no issues of any kind when the computer is running. 

The problem is when starting up. When I press the power switch, the fans and power light come on but nothing else happens. The start-up screen does not appear and the hard drive doesn't load. It just sits there forever. 

The only way I can get it to start is to turn it off and on until it does. Often it starts on the second attempt and loads normally. Sometimes it takes 2 or 3 or more tries. Eventually it starts and everything seems normal. Does anyone know anything about this? Is it a problem others have encountered? What could cause this?