Import from Word is... never perfect. Even a very clean, well-constructed Word doc (if that's not an oxymoron) is likely to have oddities in the styles when imported, at least without predefined ID styles waiting for it.
First, always import Word docs using Place, not via cut-and-paste or any other method.
When importing, be sure you check the "Show Import Options" box in the file menu (very small, to the left bottom). This will bring up a comprehensive import/mapping menu that can be used to fine-tune the imported styles and how to handle things like typographical quotes, text overrides, and more.
If the task is a one-shot, import using the Word style definitions, then adjust the styles in InDesign. (If it's a repeated operation with similar documents, you can build a "master" document for import that has the styles pre-defined, and make sure they are mapped correctly in the menu at import.)
But all this assumes the Word doc is cleanly formatted, with a paragraph style applied to every paragraph, a character style used for ALL text formatting and overrides including things like Bold and Italic, and NO spot formatting (grab-and-click) anywhere. The Word ecosystem actively encourages bad practices (some books even sneer at things like styles!) and if you have an ongoing workflow, you can make it much easier to manage by developing the same rigorous skills and practices used in InDesign when formatting the Word docs.
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