iPad randomly sent me to lock screen

iPad randomly sent me back to my lock screen after the screen went blac for like 1 second, it showed the little buffer circle too for like a second before sending me to my lock screen. I had to sign back in my app had to be reopened. What could have caused this? Is that bad? I got this iPad for Christm and I’m worried I somehow messed it up, should I be worried? My iPad model is the A1882 The new 2017 edition/model I believe. I was using iOS 11.3 when this happened and immediatly updated just in case