Mihawk never said that. It's what the Chefs at the Baratie assumed.
Go read chapter 50 where the Krieg pirates ask Mihawk why he keeps picking on them, and he tells them "for fun."
Also, go read chapter 53 where Mihawk tells Don Krieg that he was going to take his head, but is no longer going to because "he had his fun for the day." after he fought Zoro. Meaning he was bored, and was only after the Krieg pirates, because he was looking to have fun.
It wasn't because they woke him up from a nap. You should probably take Mihawks word over the Baratie Chefs assumption.