I'm going to speak for my guy here and I'm sure he'll agree with me. He LOVES when I wake him up with a blow job.
I love doing that to him too. He'll be fast asleep, snoring away and I'll see that tent his erection is making under the blanket. I'll carefully move the blanket and slowly make my way down his body and slide him down my throat. He'll snore for another moment or two before I get going and then it's an instant 'whawhoaohhhh.." and that is my favorite sound to hear.
He generally gets way more into it when it's a surprise, and when it's random and not something I'm just doing in the motions, I get way more into it too.
Surprises are always good when it comes to oral.