[Dayrion]

I think, it's because OnPlayerUpdate(playerid) is called at least per seconds. If you do an action, OnPlayerUpdate, will be called. So aiming something, shoot, walk, drive, etc .. call OnPlayerUpdate(playerid) like every 0,5 sec (IT'S NOT THE EXACT VALUE).

So, I think you should add a new variable like warnedPlayer[playerid] and this resetting every minute or 2 mins, etc..
I hope this helped you!