I've noticed that every now and then my car jerks into Reverse.
Does so when the car/transmission is cold, about 15% of the time.

5 speed FWD KJ2.

Just wondering whether this may be a sign of anything worn out, or possible failure etc?

Bump?

OK - since no-one has answered, here goes... I don't have direct experience with Magna autos, but once I did have a Range Rover with a horrible Chrysler Torqueflite 3 speed auto. I changed the trans fluid. The specs said Dexron III. I couldn't get type III, but could get type IIIA (maybe it was type IV - cannot remember). I thought "what the hell - newer fluid secs must be better! Whatever, the gearchanges were a lot crisper with the new fluid. However, when it was cold, and I was reversing out of our driveway, it would grab/slip/grab/slip something terrible. Only when it was cold - when it warmed up it was very smooth. I inquired from Mobil and was told that the new fluid had different friction characteristics and that this would cause the problems. I sold the beast not long after, so I never knew if it improved with age or not.

What type of transmission fluid are you using? I know that the transmissions are sensitive to the fluids used. Other than that, maybe it is time to change the fluid anyway?

The fluid is genuine Mitsubishi SPIII, flushed about 12,000km ago.
I am not sure if it's an rpm thing, but what I am mostly worried about is the wavespring as I know it is on the Reverse band?

Had this once before... turned out to be a fuse issue! I was honestly very suprised, but the problem was solved

Which fuse if you know?
And was it all the time or every now and then?