An unspecified number of months; a few months or several months (used when the exact number isn't specified).
そのプロジェクトは何ヶ月かかかる見込みだ。
That project is expected to take a few months.
何ヶ月か前に引っ越してきたばかりだ。
I moved here a few months ago.
彼とは何ヶ月か連絡を取っていない。
I haven't been in touch with him for several months.