I had a lot of shot anxiety initially, which is why I started on gel. When I switched to shots because gel was too expensive, at first it just took me about 15 minutes to get it over and done with. Then I went through this really weird period where it would take me like 5 hours. Nothing traumatic ever happened to me to cause it. It was just this weird period where I had a lot of dread about it.
Don't remember exactly what helped me get over it. I do think having a firm routine helps. So making sure the time of day you do it, everything you do before, getting stuff set up, etc. is exactly the same I think helps normalize it.
I do remember giving myself time limits, which was pretty effective in helping reduce the amount of time I was taking. At first I'd put a movie on and tell myself that my shot needed to be done by the end of the movie. Then, hour long TV shows. Then, half hour TV shows. Then, a song or short YouTube video. Now, I don't need any of those things but occasionally if I mentally feel myself putting it off later and later in the day, I might put on a video while I do it.