Hi there and welcome
Can you tell me which version of windows you have installed on the Dell?
Power off the Dell, then power it on and keep tapping F8 until you get to a menu
Tell me if you can get to this menu please.
It the motherboard, this is clear then.
It will be a capacitor that's failing an causing the chipset to restart or the voltage regulator. This is not a software issue
I am really sorry about this and you are going to have to return the Dell to have the motherboard replaced. It will be covered by the warranty if this has not expired, and the replacement will be done at no cost to you.
I am really sorry about this, and if you have problems, or would like any additional information or assistance, please do not hesitate to let me know.
And if you can take a second to rate my service, that would be greatly appreciated.
If you need anything else, please let me know
And please remember the service rating.