There are several passages in Scripture that suggest that human beings are still alive/conscious after being separated from their bodies (because of death or due to some sort of out-of-body experience). For instance:
The Rich Man and Lazarus (Luke 16:19-31)
Saul's conversation with Samuel's spirit through the assistance of a medium/spiritist. (1 Samuel 28:8-19)
Jesus talking to Moses and Elijah during the transfiguration (Matthew 17:1-8)
2 I know a man in Christ, who fourteen years ago—whether in the body I do not know, or out of the body I do not know, God knows—such a man was caught up to the third heaven. 3 And I know how such a man—whether in the body or apart from the body I do not know, God knows— 4 was caught up into Paradise and heard inexpressible words, which a man is not permitted to speak.
8 but we are of good courage and prefer rather to be absent from the body and to be at home with the Lord.
21 For to me, to live is Christ, and to die is gain. 22 But if I am to live on in the flesh, this will mean fruitful labor for me; and I do not know which to choose. 23 But I am hard-pressed from both directions, having the desire to depart and be with Christ, for that is very much better; 24 yet to remain on in the flesh is more necessary for your sakes.
- The apostle John, who claims to be "in the Spirit" multiple times in Revelation:
10 I was in the Spirit on the Lord’s day, and I heard behind me a loud voice like the sound of a trumpet, (Revelation 1:10)
2 Immediately I was in the Spirit; and behold, a throne was standing in heaven, and someone was sitting on the throne. (Revelation 4:2)
3 And he carried me away in the Spirit into a wilderness; and I saw a woman sitting on a scarlet beast, full of blasphemous names, having seven heads and ten horns. (Revelation 17:3)
10 And he carried me away in the Spirit to a great and high mountain, and showed me the holy city, Jerusalem, coming down out of heaven from God, (Revelation 21:10)
I'm not sure if this list is exhaustive (edits are welcome), but at least these are some of the most notable examples in my opinion. How do Christian mortalism advocates make sense of these and similar passages?