ROFLMBO Nope, it doesn't stop! My son is 4yrs old and I swear every time he is naked it's like there are little magnets in his finger tips and then ZAP! There they are on his package. Pulling and tugging in a way that would bring a grown man to his knees!!!
Summer time is worse, they get sweaty and stick down there so make sure his underwear isn't too tight. My son kept grabbing at his one day and he told me his wewe was stuck to his leg! I found boxer briefs helped my son this year so far and some of his underwear was too tight according to my hubby. If you think that is the problem, you could also try some baby powder there too.
Otherwise just keep reminding him to try not to do it in public. I ask mine if he needs to go potty and if he says no then I tell him to stop grabbing at himself.
Good luck!
S.