Why do some guys suddenly put their head down when talking to me?

Anonymous
I encounter this when buying things from them.They look several years younger than me.I am talking to them and asking for a particular product and they suddenly put their head down and look at the side or the ground.This really makes me so uncomfortable and I find it difficult to carry on my conversation with them.I am not flirting with them or anything.Why do they behave like that?Is it because they don't welcome me to buy from them?
Updates
+1 y
I am their regular customer by the way.
Why do some guys suddenly put their head down when talking to me?
6 Opinion