Does anyone else have cats whose head drops when they fall asleep?

I was thinking about things my cats do that make us laugh.

In the evening they like to sit with us when we watch TV. Now like most cats
they sleep a lot but remain alert. However there are times when they fall
hard and fast asleep, and I mean hard and fast. The first sign is their head
starting to drop - like when you nod off as a passenger in a car. To begin
with they raise their heads with a start, then progressively it gets lower
and lower. Regularly Yash (the male) ends up with the point of his nose on
the leather sofa and can't breath properly, it doesn't wake him - he just
snores. Boudica (the female) usually manages to aim for my lap or in the cup
of my hand. I can move her head around like she's a rag doll (to some
extent) and she doesn't even flinch, never mind wake up. I only know she is
still alive because then she starts twitching and chattering like she is
dreaming about catching birds - they have to dream because they are both
hopeless hunters! I mean how do you expect to catch a bird if you yell at it
first?!

Moi