Could be coming from several sources, but at the root it is from mechanical isolation or, possibly, from the slicing software. I've hear that Slic3r has some issues with this, I notice it on my prints but not as bad as what you show on the photos so let's see the mechanical part.

As Maggie said, check your printer to make sure is tight and smooth, check that your hotend is not wobbly, if you think it oscilates too easily you can try to brace it, specially if it has things attached to it like a fan and duct.
The other thing you can try is changing the acceleration values in your firmware, by reducing the values you should get smoother ins and outs during changes of speed or going around sharp corners, that should reduce oscillations on your printer.

I just checked the website for your printer and I see now that it uses an X-Y table moved with belts, one thing you should check is if the belts vibrate when printing, you can either tighten them or add some type of idler to them.