If you don't want your activity to automatically start upon scanning a tag, simply don't register NFC related intent filters in your app's manifest.
But what if...
... you did not register any NFC related intent filters in the manifest but instead stored an Android Application Record (AAR) on the NFC tag. In this case your only option is to not use AARs.
... you now can't display the tag's data in your activity, because you do not receive any intent upon scanning an NFC tag. In this case, you should have registered for the NFC foreground dispatch system instead of registering an NFC intent filter in your app's manifest.