I just experienced this the other day about 30 minutes into my run. I've never had this happen before. Well, I take that back - I remember it happening when I was in high school! I ignored it and it went away after about 10 minutes, but it was pretty uncomfortable while it lasted.

What causes this and is there a way to get rid of it when it happens?

my gym teacher used to recommend sort of lifting your rib cage up by standing up tall and inhaling, and then plopping your ribs back down as you exhale - in an attempt, I guess to get out whatever gas has been trapped there and is causing the side stitch.

not sure how valid that is, but you could try.

I just keep going. They eventually go away on their own like you found out anyway. Once you get more used to running they won't happen as often at all. I mainly will only get them now when it is really hot and humid but not always even then. Good for you for already being up to over 30 minutes!!

Breathe in through your nose and out through your mouth. When you breathe out through your mouth, try to "purse" your lips. I found that tip on a fitness site. It has something to do with your liver but I cannot think now what. Anyhoo, it works! I run daily.

I get them occasionally when I run, what works for me is to raise my arms over my head for a little bit, and also tightening my stomach muscles.

I was always told it was your spleen.