The natural cycle..
It wakes you up to prepare you. The problem for us is that we are sensitive due to the anxiety and our cortisol is spiking more anyway.
Some find it easier in the morning and worse at night so it's not a given but the reasons why are easy to point to.
Get up, get moving, get your body metabolising chemicals. I find this helps greatly, do some chores, have something to eat & drink. It subsides.