I have experienced the problem on battery and also when plugged into either of two different official Dell power supplies (one that came with it). Nothing is plugged into the computer at all, other than the power cord.
I don't use any peripherals and I use WiFi. All of the diagnostics tests pass, all windows updates, BIOS & drivers, etc are up to date (I check Windows Update, Dell Update, and Intel updates regularly). I didn't experience the problem as often but I have noticed twice over the last week or so, so the problem is not gone. This used to happen at least once per evening I used the computer and I worked with Dell Technical Support to uninstall the Killer networking software and install the latest software from their website. After anywhere from 2-10 seconds or so it goes back to normal as if nothing happened. When it freezes, the mouse does not move, the keyboard is unresponsive, and even CTRL-ALT-DEL does not do anything. Obviously I only notice this when I am using the computer, and I am usually doing things in Chrome, but it doesn't seem to be related to any particular websites. I have an Alienware m15 several months old and from the get-go, I have had a problem where it intermittently freezes for several seconds.