Gentlemen, good morning!
Usually when I am playing a game, I press "X" (home) button, turn off my console and, when I turn on again, just continue EXACTLY where I left.
But sometimes when I turn the console on, it does a full boot (green screen with loading dots, then xbox logo on black screen, then home screen) and the game has to load all over again, recovering from last saved checkpoint.
Anyone knows why? I didn't find a pattern here...