Why do I get more flirty/horny at night? Is it normal?

So I’m not really a flirty person I’m more of a joke around and make me laugh to win my heart, I don’t like cheesy stuff much but once 12 AM hits I’m all for it and I’m being like overly emotional and flirtatious. And I get way more turned on by things the later it gets. I really don’t understand why I’m like this so if someone could give me some possible explanation I’d appreciate it lol