restart

i restarted my mac and then an apple logo appears.the bar is slowly filling up.when its about 70% filled it stop there and a gray screen appears.and after a few minutes it shutdown and restart itself.and again same thing happen.i search for first aid at youtube.everything did not solve my problem.and then i waited for how many hours .i did again the advices from youtube and after a while my problem is solve.But when i have an update it needs to restart again.and again same problem occurs.by the way there is no light from my keyboard when those things happen.