Are you unlocking with a fingerprint? Perhaps you are pressing too long. I find that when I hold my finger on the print reader too long, one of the apps on my quick launch bar opens. Fingerprint only requires a light tap.
@BC10 You probably have a malicious 3rd party app installed which is doing this.
One thing that you can try to identify the cause of the pop up is to use Good Lock's Nice Catch module. Samsung's Good Lock is available in the Galaxy Store (NOT the Play Store). Open Good Lock and install the Nice Catch module. Open the module and enable it. Enable items like "Toast history", "Detect commercials", etc.
But you may end up resorting to deleting 3rd party apps until you find the culprit.
That sounds like a shortcut, maybe. Hold down on the screen in an empty area. Click on "Wallpaper" and style." Then click the top-left "Lock screen." You will see two quick-open apps on the bottom left and right of the edit screen. Click on the area where you see the Play Store and switch it to something different.
