Hi Bennuendo,

You can disconnect any devices such as printer, USB flash drives and external hard drive. Remove any DVD or SD card inserted and try to restart the computer.
If the issue still persists,try to load defaults in BIOS which can help you fix the issue. Turn off the computer. When the Dell logo appears, press <F2> key 2-3 times, a BIOS utility will appear. Use the arrow keys to highlight 'Load Defaults', press Enter and press 'Y' key. Select 'Save and Exit Setup'.
You may also try to run the diagnostics to check the hardware functionality:
1. Power off the computer
2. Restart the computer; tap F12 on Dell logo 2-3 times.
3. This will take you to One Time Boot menu.
4. From the list, select 'Boot to utility partition' using the down arrow keys, press 'Enter'
5. Click 'Express test'
6. Run the test, if you get an error code please make a note of it and continue testing.
7. Please share the error code if any.

You may also try the video drivers update by referring to this link:
Video drivers
Click on 'Download File'>> click "Download Now'>> Click 'Continue' on User Account control if prompted>>Click 'Continue' on the Application prompt>> Click 'OK' on Select the folder where you want to unzip the files to( Make a note of the folder location)>> Click 'Yes' on the next prompt for folder does not exist>> Click "OK' on All files were successfully unzipped. >> If the installation wizard does not appear, go to the folder location>> select the Setup file >> Right-click and select 'Run as Administrator">>Follow the installation wizard instructions.

Hope this helps.
Please reply if you have any questions.