New Macbook Pro freezes and sleeps

Hi all - First off i'm a neeb and recently converted from "Windows" to Mac!

I have a brand new <3weeks old MB PRO

Model Name: MacBook Pro

Model Identifier: MacBookPro11,4

Processor Name: Intel Core i7

Processor Speed: 2.8 GHz

Number of Processors: 1

Total Number of Cores: 4

L2 Cache (per Core): 256 KB

L3 Cache: 6 MB

Memory: 16 GB

Problem is the system randomly black screens with the keyboard and back light illuminated.

I am on my 4th call to apple support and the its just been returned from Apple shop genius where they

couldn't find anything wrong with the hardware.

It seems to happen when I am interacting with my NAS or creative cloud file backup.

The mouse freezes and the screen goes black. The keyboard still works and I can still hear

email and txt messages etc.

Its driving me crazy.

Hopefully someone can help me!!

Thanks