I worked graveyard shifts at a gas station for a year or two. My general experience beyond what other people have said--good commute, fucking with your social life, taking its toll on your body, all that--is that working graveyard shifts is lonely. I cannot understate how lonely it got; there were stretches of multiple hours where there were no customers at all, and it was just me and the long list of nightly chores I had to do (mopping floors, prepping food for breakfast rush, restocking shelves, etc., etc.). Not having any human contact at all fucks with your head something fierce, especially when you mix in sleep deprivation and your body rebelling against the normal sleep rhythm into the mix.

My advise is that if you're going to be working night shift all alone, get into podcasts. Having a radio that I could use to listen to NPR was the main thing that kept me sane, because I could at least have a human voice to listen to and keep my mind somewhat engaged.