Thanks for that. The first thing I would try is updating your graphics card driver. It looks like you have version 353.54 and the latest for you card looks to be 378.49.
Secondly, take a look at the Nvidia software on your system and see if anything is shifting the graphics card from your Nvidia to the on-board card when UE4 starts up. This is sometimes the issue with Nvidia cards on laptops. I think the program is called Optimus.
Let me know if either of those make a difference.