Outofwhack,
I remember the first time it happened to me, very disconcerting, but in my case I was a long way from anywhere in the Canadian bush. Word from engineering was "anytime it happens, shut the engine down straight away, go inside and have a cup of coffee, wait about 10 minutes and try again".
The clutch always engaged normally second time around.
I'm going back to the 70's here so can't remember the exact conditions at which these things were done. This company had operated several 47s of different marks for fifteen years at that point, winter and summer, and had some very experienced guys maintaining them. I was around 47s for three years and never heard of any safety concern with this phenomenon nor can I recall any clutch problems which may have come because of it.
Also, for your info, below a certain temperature on moist days, on the first start of the day, we pulled one set of plugs [left or right, didn't matter] and put them in the oven to warm them. It made starting much easier as icing of the plugs was an occasional problem as well.