If I haven't downloaded any new maps lately (that I can remember) or if I just get really bored, I start going through my entire list of songs trying to find a map I gave up on, or anything new. Occasionally I may scan for maps that I have crappy accuracy on (osu! standard). By the way, I only have about 1800 maps, so it's not like I spend weeks going through every song o3o
I have a tendency to hop on osu! when bored or to get distracted from work to see if any of my friends are on.
During breaks, I tend to move the fruit catcher according to the rhythm in a variety of ways, as if I were practicing jumps (Ryuuta dance? lol)
For restarting rapidly, I will often hit escape, then quickly move my mouse over and click the Retry button in time with when I would've hit the next note. Sometimes my mouse will be over either the continue or quit buttons and I would accidentally click them.
There's a threshold of whether I will shiver or not depending on how much I've played osu! in the past while, how much I've played earlier that day, and on how difficult the song is. I rarely shiver if I've played osu! a lot in the past week.
I apparently/often perform better when being spectated.