Probably a bad fan, they do fail at times. Some of the fans I have seen plug into the GPU board, make sure it has not come loose. Also run diagnostics (F12 immediately at boot) and see if you get a fan error. On a new system I would be calling Dell tech support as they may have to replace the GPU.

You could try removing the fan and oiling it but thats only a temporary solution.

Synthetic motor oil is the recommended solution with an oiler with a needle.

https://www.amazon.com/dp/B077BLLMBS/

The real solution is to replace the fan.

I bought a GPU shroud on HW swap with a fan that didn't turn once.  Disassembled it and found a machine screw jammed stuck inside the fan.  Not saying this is your issue, there could be a number of potential issues with yours.  I can't remember if Dell puts the stickers over the shroud to warn you about removing them.  But do keep in mind that if you disassemble the GPU that technically would void the warranty and could be a basis for a denied claim.  Probably safer to just pull call in to Dell for warranty repair/replacement if you're still under warranty. 

+1 on call Dell Tech Support. I had a fan fail on my 3080. It would try to spin and pause, then try to spin and pause.

1. They will use Support Assist for Diagnostics

2. Make you record a video and email it (open case, use light and phone recorded)

3. Install HWInfo64 while running various benchmarks.

4. Unbelievably, they didn't approve warranty claim at first because temps were within range! I told them I'm in an AC room with case open because 1 fan is dead. I made analogy, "Just because a Airbus A320 can fly on one engine doesn't mean it's good for the plane! My 3080 is going to fail 1-day after warranty expires this way!". So, I closed up case, turned off AC, and let it get toasty... got an appointment for 3080 replacement (also was NOT LHR).