Re: nudity
Well, I learnt that it is sunnah of Prophet Muhammad :saw: to say certain duas, such as before entering the bathroom/restroom (i.e. seeking refuge of Allah (SWT) from shaitaan and khubaith), and while leaving the bathroom (thanking Lord for relieving or getting rid of what was not healthy for the body). Other duas such as before going to bed i.e. Oh Allah, I die and come back to life in your name. This is to acknowledge God’s complete sovereignty on our life and death. Waking up in the morning is like coming back to life.
I think if you read the thread in details, people who have posted duas have also posted the reasons quite clearly, including the reason for saying a dua before making love.
And only Allah knows the best!