I'm no expert on this topic and have just been playing around with a Minolta XG-M for a couple of years. But I had the exact same issue that this post describes and after finding this post in search of a fix, I have actually managed to fix it myself.

Just as described in the question, I had replaced the batteries to my camera and turned it on to find that when I pulled the advance lever the shutter would automatically release without pressing the shutter button. Before taking it apart I decided to experiment with the power settings and advance lever to see if I could see what the cause might be. After experimenting for a while I found that a combination of steps lead to my film camera's shutter functionality being returned to normal.

1. I turned my camera on
2. I pulled the advance lever and the shutter automatically went off (as expected)
3. I unscrewed and removed the battery compartment (I had not turned off the camera)
4. I turned off the camera
5. I returned and screwed in the battery compartment
6. I turned on my camera
7. Pulled the advance lever and the shutter no longer triggered automatically

I understand that I am writing this as if it is some kind of exact science, most likely whilst messing around I unknowingly corrected something completely unrelated that had gone wrong. But ultimately these steps lead to the problem being solved so I thought I'd provide as much detail as possible to anyone who might come across the same issue.