Well, the simple and proactive answer is for the PAX to mention to the FA's upon boarding that you do or don't want to be woken for the meal orders. If you have already ordered, and you fall asleep, procedure is to wake you for a hot meal delivery but not a cold one. Again, letting the FA know ahead of time will avoid any ambiguity.

That being said, many FA's will wake everyone because they don't want to be bothered by a bell from someone just waking up while they're trying to finish the service. Me, I'll let you sleep in the hope that you don't wake up and I get to eat your meal. See, everyone has their own little agenda.