Perhaps make this an option only.
My characters would always be wearing armour to sleep, even the one who wears heavy armour would switch to another type rather than nothing. It would be immersion breaking for me to be wearing bedclothes in a strange and hostile area, wearing them in a dream would make it obvious that the dream was not to be trusted. If later on we have an inn room or something, then the bedclothes would make a bit more sense.
