For S, I chose "singing," but not the kind of singing you see here:
I'm talking about the kind of singing you do when you know nobody can hear you (a.k.a. make fun of you!).
I wouldn't even dare sing in the shower. But the car? All bets are off.
Especially if you just discovered a movie soundtrack you listened to over and over when you were a teenager (Streets of Fire). And you still remember all the words to the songs!