In the old days I used to paddle my white water kayak in flat water and it would spin out either way randomly for no reason. As rudders or even skegs weren't prevalent I just got used to it.

I got into a routine, as soon as the kayak started to spin - say to port, I (think) would lean the kayak to port and do a sweep stroke. That usually set things straight untill the next occurance.

If the well timed sweep stroke doesn't work or becomes too irksome a little skeg addition may do the trick.