it's okay to leave them without cloth...my house shih-tzu also leave it like that even after cut short hair...they will try to sleep near you when it's cold...if your shih-tzu cannot reach you, maybe you can prepare a blanket by it side...

yeah...nowaday all dog lovers sleep with their pet in same bed, sometimes i'll accidentally sleep on the shih-tzu too...hahahha
dunno in future we will sleep with our kids or not....

that's a reason why dog sleep in air-cond room fur looks better, that's because when they feel cold, the fur will become fluffy and thick to keep warm... same to winter country fur kids....