Depends who you are and what you plan to do during the day. If you're working in an office or in close connection with other people, you'd better be sure to shower in the morning. Otherwise you can please yourself.
I suggest night time after a long day all your skin cells come loose get dirt underneath and a good shower will make you feel clean when you climb in that bed. if you feel like it take a shower twice a day.
Depends upon where I live, what the weather is like and what have been doing. Up North in the winter would take warm shower at night, too cold in the a.m...brrr., down here in the Tropics usually take one twice a day and if its really hot and have been working hard/sweating; up to 3x. So as has been said it depends....:-)
Me shower is okay at any time. but it is known the taking bath relaxing your bones so if you have ace take hot bath that would relax the you. listen to soft music either shower or bath that would put you in relax state of mind too.