Yeah for some reason my anxiety heightens at night. I think this is due to the fact that everything is quieter at night and we have more time to contemplate or think about our past and future. During the day we're busy doing things, or have other things on our mind that are preoccupying us, but at night everything sort of crashes down on us. Anxieties about the next day, or having trouble sleeping, or waking up in a cold sweat at night are all things that happen at night because the brain is trying to relax when you're stressed out.
My first panic attack happened at night and I also had to call 911. I was convinced I was having an allergic reaction too.