I have a toshiba satelite l555d and sometimes

Hello,
m laptop sometimes doesent turn on corectly other times it turns on perfect when it does turn on it says f1 to resume f2 to setup so i push f1 and it always delites my time and date configuration and when it doesnt turn on it shows that it is on by the leds glowing and the cpu fan going and the hdd going but the screen isnt on i just need some help.