I've always had this problem too, except for my last sickness hit me around 6pm. I think it has a lot to do with the timing and the incubation period.. 24-48 hours after exposure. You don't get exposed lying in bed the night before, right?! It's usually during the day. I think that's how most end up hitting in the middle of the night because of that time window.

Maybe. Haha I'm not too sure! Makes for some crazy anxiety though... never knowing what may happen in the middle of the night and if you do wake up, you freak out even if it's not because you are sick. Bleh