Inspiron 13-5378, No bootable devices found.

When I was using my laptop (it was working perfectly a few hours ago) it’s battery was low enough that a screen in SupportAssist said that the battery was critically low so when I tried to reboot after letting it charge for a bit, it kept wanting to do a RAM test and when it would finish, I would hit Esc so it would reboot. I would end up getting to that screen yet again so this time I just rebooted and sure enough, I was back st that screen yet again. I did the diagnostic preboot or whatever it’s called and after it was done, it rebooted the computer and now I keep getting the No bootable devices found screen. What do I do? How can I fix this?