I have a Panasonic GH3. It is very difficult to partially press the shutter button to focus as it often takes a picture at the slightest pressure. I thought this was my inexperience, but a couple of other people tried it recently and commented that it was overly sensitive. I don't suppose there is a setting in software to lesson the sensitivity is there? How can you tell if the shutter button needs adjusting?
To find out if this is normal, your best bet is to try another GH3, say in a store. Without trying it out, I cannot tell if it is normal but it could be. In my review of the Panasonic GH3, I described it this way:
Indeed, the halfway-point is soft. If you push a little too hard you can easily miss it. This is why it is important to at least read about a camera's ergonomics if you cannot try it yourself.