Always in the morning as i don't feel "fresh" when i wake up if i showered the night before. Even though going to bed freshly showered is such a nice feeling
If I can fall asleep without showering first, I'm either just dead ass tired or drunk af and passed out on the couch...like it's a must before getting into bed for me. And I don't feel fresh during the day if I don't shower after getting up, so usually I have a really quick 3-5 min shower when I get up, too.
Morning. But I do both if like I did a heavy activity in the morning/afternoon so I must shower at early night (5:00 PM-6:00) to feel fresh and it helps me sleep faster.