What causes this?

I will just add that this is basically a "free antitheft device."

It requires a simple trick to start it (sometimes...), and only you know it.

So long as you know what's going on, and how to rectify it if it gets worse, it's not a problem. Any young kid wanting to go for a joyride would be completely stymied by it.

I had a couple of cars "back in the day" with misaligned neutral safety switches, that would only start if I pushed the selector just a bit further toward Park.
I never fixed 'em. It's like extra insurance.

– Eric