Lost 60% of my traffic suddenly and don't know what to do

I have had a blog since 2017. It's been consistently growing for the last 2 years. On Friday, December 30th, around 5 PM PST I went from around 700 users an hour to 200-300 users an hour. It was sharp and drastic. No steady decline, just one hour it's normal, the next it's not.

Of course, I hoped it was a lack of searches given New Year's Eve. But the new average of around 200-300 unique users per hour has held for the last 36 hours or so with no variance, like suddenly it's the new normal.

I went from roughly 10k users a day down to 4.5k users a day.

I changed nothing about my website. I have no manual actions against my site. I don't use spammy practices.

I have no idea what's wrong and I'm freaking out a bit. I know it's not a lot to go on without being able to click around and investigate, but does anyone have any ideas on what I could check or do about this?

Thanks.