when we pronounce the question: "Do you want some coffee?" we usually only stress the words "want" and "coffee". Am I right? As far as I know the determiner "some" is unstressed as long as the stress is not shifted for special emphasis. Am I right? Any suggestion is appreciated. Thank you!
Yes, that's correct. You would only stress "some" if it was the most important part of the question - "Do you want some coffee or a lot of coffee? In that case, "coffee" would be unstressed.