It's usually a combination of things - being it situations where I have to present as conventionally male for any length of time, and feeling envious in the company of certain women. Also body issues, such as going more than a few days without shaving my arms and legs, and seeing hairs on my hands and wrists. The loss of my hair in my thirties wasn't great, but I'm resigned to hats and wigs when necessary.
I think it may be age related as well, as it's really started to hit me in my late forties, and I now feel it's too late to do much about it. When it's bad I'll treat myself to a new dress and a bottle of wine, or spend a couple of hours in the bath shaving everything.
I'm a male-bodied female btw, in case that isn't apparent from the above. Not transitioning as such, just a hybrid!