At this point, I recommend doing a full shutdown, and doing the POST Boot Test, (*Option 1 in my previous answer.*)
As I said, I'm not currently a Dell technician anymore, but I still love their systems.
The POST Boot Test can take anywhere from 10 to 20 minutes in most instances, and will test hardware, software, and configurations essential to getting your system to hand off to your OS, such as Windows 8.1 in this case with your laptop.
NOTE: The Extended Test option can take an hour or more, depending on the tests the system runs.
If you have any further issues, please attach the .log file from the POST Boot Test. (I don't remember specific locations, but you can search for it with Win +Q and type in *.log, and it should find any log files, which then you can attach to your message / reply on this forum.)
**Further Note: Some newer Dell laptops do not have a log file that appears on Windows. If your system finds any errors in diagnostic mode, it is advised to use a cell phone or other device with a camera to take a picture of the error message, or write the error message down, and then research it on a computer that has access to the internet. (This assumes that there may be cases where the laptop does not connect to the internet.)