when a new notification is received, it is announced once on the Samsung device with a tone and/or vibration, depending on the sound mode. with the "notification reminder" function, you can set an interval that reminds you of the new notification at regular intervals. the reminder can be activated either for calls and messages only or for all/selected apps.

Android 10 (One UI 2.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Accessibility
Step 3:  Tap on  Advanced settings
Step 4:  Tap on  Notification reminders
Step 5:  Enable or disable  Notification reminders
  1. Open the Settings
  2. Tap on Accessibility
  3. Tap on Advanced settings
  4. Tap on Notification reminders
  5. Enable or disable Notification reminders

Samsung Instructions