I frequently think about what makes me want to dress.
I often go months even a year or so without it even being an issue or a desire than all of a sudden it becomes a necessitate. A requirement that I must address before I can even set forth in my standard drab life. I finally succumb to my deep setted emotions and dress to portray the beautiful sexy women I always admired and loved. Afterwards I feel like I have achieved my goal, I can then finally go about my life.
For me I find that stress in my normal day to day to be my #1 trigger and the second is reminders of bad moments of my childhood 1 &2 are likely related.
I have many others but lets hear yours.