My phone keeps ringing a notification every 64 sec. I have blocked ALL the app notifications. Still happening. Where to look to stop it? Android moto G ver 5.1 patch level 2016-03-01
There are a number of reasons this can happen. Some power-saver apps, like "GSAM battery monitor" can emit an audible tone, but not put anything in the notification bar. I also found reports of apps where the "Notification Icon" setting is separate from the "Notification Sound" setting.
Your best bet is probably going to be to install a Notification History app, than can log every app which issues a notification to the system.
Welcome to Android Central! Is it the default tone you're hearing, or a completely different one? If your NFC is on and it's detecting something nearby with a NFC chip (like a credit card, especially if it's in a wallet case for your phone), then that might give you constant notifications.