Depends on how you feel. If you live somewhere where nights are hot, then a night shower might help you to sleep. If nights are cold -- showering is just unpleasant. Soemthing similar thinking for morning: you might not have time for a morning shower, being in need to get up at 5:00. Or you might like a morning shower because it'll grant you an additional 15 minutes of freshness at 35 degrees morning.

Just use your head and feel your ass.