1) is there a story you’re holding off on writing for some reason?
Mostly, I'll write down a sentence or two, or maybe a summary and then just lose interest, either almost immediately or over the next few months. That's usually the reason why things don't get finished.
But there are two ideas that I'm hesistant to start/go further because they're big AUs and represent a huge commitment. One's a Lokane AU, where Jane gets imprisoned on Asgard for her own safety and becomes close with Loki because he's the only intelligent conversation she's able to have for a month. The other is the lengthier version of a WEaT/TDF fix-it/AU where Missy's backseat driving means the TARDIS doesn't land on the colony ship, saving Nardole and Bill from their fates, but she and the Doctor still find their way down there and find the Simm!Master. And at least one of them dies down there, but there's a lot of feelings and tension, and the action is split between the colony ship and the TARDIS, where Nardole and Bill are trying their best to save them as well.
Both are complex and plotty and will definitely be lengthy, with lots of PoVs shifts. So yeah, commitment.
5) character you were most surprised to end up writing
I don't think I get surprised necessarily. Frustrated that my starting character wasn't the right one and having to start over. Soometimes I'm surprised that I want to approach a story from a particular character's perspective, but never 'wait, where did they come from?'
I didn't think I'd end up caring quite as much about Natasha's friendship and familiarity with Tony (in a 3/4 finished MCU fic), so tempted to push Holmes' relationship with Morstan further than intended (a 5+1 casefic ACD Sherlock fake married thing that's a behemoth), or doing River/Thirteen breast worship, which is surprising because I didn't ever see myself writing that pairing as much as I think it's a cute dynamic. (Though that's pretty much why I decided on doing it.)
15) why did you start writing?
This is the easiest to answer. I was homeschooled until I was six, and I was taught how to write by being asked to tell stories. So it's something I've always done. Why I've continued? Partially spite - wanting more of the stories I want to see in the world. Partly I just love words and finding the right one, the right order, to desrcribe what I'm seeing and feeling in my head. Again when I was little there was a segment on radio on the weekends with an etymologist; where words come from and how they're used. And I love that, I love word play like puns and spoonerisms, and how 'chewing someone out' and 'eating someone out' are two very different things.