Why is my smoke simulation having a weird moire effect?

Hello everyone!
I am trying to make a simple smoke simulation and it renders out with a weird moire effect?
I’m using Cycles Render with my GPU
This is how it looks:


If I lower the density it fades a little, but the effect is still there (first img the density is 20, second img is 10):


I used the settings from a YouTube tutorial in which it looks ok (https://www.youtube.com/watch?v=VmRqlsuSvsw)
These are my domain settings:


I’ve tried tweaking every setting possible, I tried rendering on my CPU, changing the lighting etc. but looks the same.
Does anyone know why is this happening? I am working on a project and I have a deadline at the end of this month and this is really frustrating! Pls help!

My specs:
Intel i7-6700 4.00GHz
16GB RAM
GeForce GTX 970 4GB - 256bit
Windows 7 64-bit
256GB SSD + 1TB HDD