White screen !!

[Housefien]

Hey , every time I start my iMac up it goes to the apple logo spinning wheel spins then it goes to white screen ?

I can get it to start up perfect if I unplug power cord hold down power button and plug it in and it starts up perfect with the fan going loud , how come it starts fine doing that but not if I normally start it ???

 

[Roman78]

I think we need a little more information about you hardware and OS.