Recently, I got a few desktops and laptops have a same problem. Suddenly, they cannot boot up into windows anymore. After the power is on, they entered a loading screen of windows, after a minute,it restarted itself. This situation repeated a few times, that is a kind of an infinite Loop of restarting. Finally, it will go to a windows boot manager. Then you can choose to enter safe mode. If you are luck enough, you can go to last restore point. I found this problem are caused by the windows update. In my cases, I had to use the restore image and did a factory reset.