Hamlet: Why, look you now, how unworthy a thing you make of me! You
would play upon me; you would seem to know my stops; you would
pluck out the heart of my mystery; you would sound me from my
lowest note to the top of my compass; and there is much music,
excellent voice, in this little organ, yet cannot you make it
speak.

'Sblood, do you think I am easier to be play'd on than a
pipe? Call me what instrument you will, though you can fret me,
you cannot play upon me.

[Enter Polonius.]
God bless you, sir!

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I believe Polonius' 'God bless you, sir!' is the Renaissance equivalent of the modern-day of the 'May I help you?' which is uttered in an icy tone with hooded lids.

In other words, he thinks Hamlet's nuts. Who wouldn't think so, confronted with so many frenzied metaphors?