My first ever caution was an U/10 player who, despite several warnings, shouted 'ooglie booglie!' every time he went in for a tackle!!
For me there are two considerations for this. Intent and if the target was actually distracted.
If there is intent but no distraction, first one gets a warning.
I have plenty of warnings which usually stops it but have card a couple of times for it in the past. The last time I had it there wasn't a single complain about the card because almost everyone had seen the warning.