startup

What is the exact model and specs of your Mac

Brand new means you just got it out the box and it already does that?

Only a few things to try:

How to reset the SMC of your Mac - Apple Support

Reset NVRAM or PRAM on your Mac - Apple Support

Restart holding Shift to enter Safe Mode, once loaded, just reboot normally and see if it works.

Also try restart holding Command R to enter Recovery Mode, open Disk Utility, select the Mac HD drive and run First Aid.

If none of those help, go to Recovery Mode again and reinstall macOS.

If not even the reinstall of macOS solves your problem, wait no more. Once you're still under warranty, turn if off, put it in the box and ask the buyer for a replacement (if still in time), or take it to an Apple Store or authorized for a proper solution.

Sad to hear that, man.

I do have one of those, the i9 5500m actually, and it's been great since day 1.

Just don't give up yet. Call Apple Support, tell your story, then take it to an Apple Store and let Apple do its thing.

16" are pretty good machines, hold on a bit more 🙂