First of all, this is potentially specific to the Panasonic G3, but as all the cameras are quite similar you may find this of interest if you are using another model, it’s certainly worth a try…
As far as focus modes go, this should be quite straightforward if the manual is to be believed:
“AFS” is an abbreviation of “Auto Focus Single”.
Focus is set automatically when the shutter button is pressed halfway. Focus
will be fixed while it is pressed halfway.
“AFC” is an abbreviation of “Auto Focus Continuous”.
This mode allows you to compose a picture more easily by continuously
focusing on the movement of the subject while the shutter button is pressed
Note: Olympus refer to these settings as S-AF (Single AF) and C-AF (Continuous AF)
So, for motorsport AFC is a no-brainer, right? Not on the G3 it isn’t, I’ve shot one day of motorsport with AFC and one day with AFS, my keeper rate increased dramatically when using AFS and it was immediately obvious that the camera was operating much more quickly in all respects. The other crucial factor is that AFC slows down the burst rate to a painful crawl if it’s stuggling to lock on, but in AFS you can hold down the shutter release and it will fire away at full speed.
In conclusion, tell your M43 camera you want to take photos of a static object and see if things get any easier.