When you load up a world, you will not take any damage for the next few seconds.

How to reproduce:

1. Go in lava and start taking damage
2. Before you die, save and quit.
3. Go back in the world

Observed results:

You do not take any damage for a few seconds

Expected results:

You should start taking damage immediately.

This can be used as an exploit.

On Bedrock Edition, you start taking damage immediately.

This can be used to avoid damage from an explosion, fall damage, lava and fire damage, and more.

Video: https://youtu.be/CYODV09zIU4