Laptop switches off suddenly, then displays no bootable device?

[Jem Cakan]

My Dell Inspiron 11 3148 Switches off suddenly in the middle of watching a youtube video. Then displays no bootable device.
I enter BIOS mode and check options in LEGACY mode. There is no USB/HDD/CD option at all. My BIOS is showing no connections to the motherboard. I then reset BIOS to default. Still no signs. I take apart the laptop, ssd is connected securely. Still no signs. I connect a USB with windows 8.1 on, I try to repair PC, it states "The drive where Windows is installed is locked. Unlock the drive and try again.

What is this? A virus? A motherboard issue? I run onboard diagnostics and it states everything is fine...

 

[Laptop_Nerd]

Hi Jem Cakan,

Please refer to this link from your other post with the same content.

http://www.tomsguide.com/forum/id-2782676/laptop-suddenly-switches-bootable-device-appears-pictures.html#16550896

Thanks