Shoud I accept an offer as editor of a journal as an undergraduate? I’ve recently received an offer from a reputable (but not top-tier) journal in my field asking if I would like to serve on the editorial board. I believe they reached out to me based on my publications in the area. 

Although this would be great experience and a way to get more involved in the community, I’m not certain if I’m qualified for the role. What would you consider while making this decision?
No, you should not accept an editorial position as an undergraduate, or as a graduate student.  It probably will not be good for the academic community, and it almost certainly won't be good for you.  There are multiple clear reasons:


Editorial work is service to the professional community.  To be done well, it requires a significant time investment.  Early in your career (meaning: until you get tenure), your time should be focused as much as possible on research.  Senior people in your field usually recognize this and editorial positions are usually offered to people at the associate professor level or higher.
The journal is probably not reputable.  I know I'm contradicting your claim, and I may be wrong in your particular case, but I will be right in saying this at least 99% of the time.  Very few undergrads know what journals are reputable.  I received a few invitations to editorial boards as a student, but not from any reputable journals.  No reputable journal in my field has a student (undergraduate or graduate) on their board.  Even if the student were brilliant (or especially in that case) point #1 above would dictate that they avoid this.
You aren't qualified.  Again, you may be the most brilliant person in your field, but that's not the main requisite for editorial work.  To be a good editor you need extensive experience in reading and writing papers.  You need a network of colleagues you know well whose expertise covers a broad swath of your field, who you can invite to review papers.  I've never met a graduate or undergraduate student who had both of these things already.


For context, I can think of a brilliant friend who published a lot of papers as a student, won prizes for some of them, and even skipped the postdoc phase, going straight into an assistant professorship at a top-notch research university.  He certainly wasn't qualified to be an editor when he was a grad student, and accepting an editorial position before he became an associate professor would have been a mistake, for all the reasons above.

Note also that if the journal invites you to apply for an editorial position (i.e., if you need to send them a CV) then the journal is not reputable and you should stay far away.  Respected journals will know who you are and have already considered carefully before inviting you to the editorial board.

You probably should not accept an editorial position when you are a postdoc, and you should perhaps think twice about it as an assistant professor.