You still have to think about what you are doing. Dressing in a private lot after hours would cause suspicion and police often check private lots after hours for drinking and drug use. I use parking lots in shopping centers that are open. I don't park way at the end where mine is the only vehicle, I park where it would seem like I am in one of the stores shopping. I keep my awareness up and if necessary, I drive away and find another place to change. And I underdress so "being naked" is minimized.
Yes, I would rather get all dolled up and stroll out the front door carrying my purse but that's not going to happen.