In the shower... in bed, but make sure they are all asleep first; and don't go making any noise.

Don't be surprised if they have the same thing on their minds as you.

Depending on how well you know them, you *might* be able to get away with just doing it anyhow, as an icebreaker. Could be uncomfortable at first, but once everyone else realises you're cool with/about it, they will probably relax and do the same.

Nothing ventured, nothing gained.