I own a 2015 15" mbp. when the computer is booting up, once the black bar is 1/4 loaded the screen goes blank for a bit then the black loading bar reappears and the computer continues loading. Its not really a big deal and my computer works perfectly, but sometimes it just really annoys me. I heard that it could be a result of file vault, except it is turned off. Any insight or solutions would be greatly appreciated.