Seemingly unrelated topics are all intertwined: First it's the counting of the Jews and then Levites. But then comes Nazir, Sotah, additional laws of stealing...
And the Levites themselves are not counted in any order, not starting from the oldest son, with one of the three sons beings counted separately in Naso instead of Bamidbor...?
Is there any explanation for the ordering here?
If I could, I'd rather phrase the question differently. To me, most of the beginning of Sefer Bamidbar is not intertwined: it is a detailed discussion of how Israel was arranged around the Mishkan. The numbers of each tribe and how they were arranged in degalim, then the same for Levi along with the jobs of each of the parts of Levi (into P' Naso), then the rules of who is not allowed to be in each machaneh, then the presents of the Nesiim to consecrate the Mishkan, then (P' B'haalosecha) the consecration of the Leviim, Korban Pesach and Pesach Sheini before they left, statements that they moved according to the direction of G-d, the trumpets for moving the nation - and then they began to move.
That all seems very sensibly arranged to me.
The question is, what are those three mitzvos you mentioned doing there? Why are the laws of gezel hager, sotah, and nazir way over here in the middle of this presentation, instead of where I would have thought they would go - say in Parshas Kedoshim?
Rav Shimshon Rafael Hirsch has one interesting attempt at an answer, see there.
Update: There is a very brief comment from the Seforno, Bamidbar 9:1: "בחדש הראשון אחר שפקד אנשי הצכא וסידר הדגלים ונושאי המשכן להכניסם לארץ וטהר מחניהם מן הטמאים כאמרו והיה מחניך קדוש (דברים כג, טו) ומן הממזרים בענין הסוטה למען תהיה השכינה ביניהם במחנה צבאותם" - "after they had purified their camp from tumah, 'Your camp shall be holy', and from mamzerim in the matter of the sotah, that the shechinah could be among them in the camp with their hosts..."
Not quite clear why those are the particular mitzvos that are needed for the shechinah, as opposed to the whole rest of Toras Cohanim, but the Seforno seems to be addressing your question directly.
