first we need some more info.... model, caliber, new or used and what does the owners manual say ?

Assuming that this is a 1911, it sounds like the mag catch is worn or the mag is not being fully inserted. Before calling Springfield for warranty service, take you time and when reloading make sure that you are fully inserting the magazine, then tug on the magazine and see if it comes out, then use the slide release ensuring that you're not bumping the mag release.

Also, do you have more than one magazine and if so does it do this with both mags? It's possibly that the slot in the mag that the mag catch uses to secure the mag is damaged. Does the mag stay in if you just pull on the slide to release it?

Take it one step at a time and you should be able to figure out if it's you or the gun, if there's a problem with the gun, contact Springfield Armory and send it in for repair.