You realise that the stranger is asking you a question. Not with words but with the most subtle nudges and touches.
You could say that the stranger is very polite - and yet beyond social norms.
You can of course ignore the question - but some part of you enjoys the challenge to communicate without words about a delicate subject.
How do you respond?
RE: Imagine the attractive fellow passenger encroaching on your space ... . - What next? Comment, and I'll pick up your story from there ...