It should only happen one time unless your device is not storing the cookie for some reason.
Push notifications are notifications that appear in the message bar of your Operating System. It allows you to get notifications through your OS even when you don't have the forum open.
Generally, you either select "yes" or "no" on time and would then have to into your preferences to change it.
I might suggest looking at your preferences and in your case, just turn off push notifications.
If for some reason, that doesn't work, let me know. I might be able to turn them off for your account (I would need to look).