Please let me know the system model and the operating system installed so that I can help you in a better way.
For laptops, turn off the system. Unplug the adapter and the battery. Press and hold power button for 10 seconds. Plugin the adapter. Press and hold Fn button and turn on the system. This will start the diagnostics on the system.
For desktops, turn on the system and tap F12 on the Dell logo for One Time Boot Options. Select Diagnostics or Utility partition to start the diagnostics.
Please keep me posted with the results.
Thanks & Regards