@Groggle: Can you check to see if your tablet is up to date by heading to Settings > Software update > Download and install, followed by Settings > Biometrics and security > Security update? Furthermore, head to Settings > Battery and device care > Memory > Clean now, then press the Volume Down and Side Keys together for around 10 seconds until the tablet vibrates and restarts.
If the issue persists, try restarting the device in Safe Mode, as this will disable all third party apps and help to determine if the problem is stemming from an external source. To enter Safe Mode, press and hold the Power button until the 'Power off' prompt appears on the screen then release > Touch and hold Power off until the 'Safe mode' prompt appears then release > To confirm, tap Safe mode.
Monitor the performance for a few hours, depending on the frequency of the issue. If you notice an improvement, restart the tablet as you would normally and uninstall any applications you have added since you first encountered the problem. Let me know how you get on.