Summary:
The player can set a spawnpoint on a lava cauldron and respawn in it. It seems that the game does not consider the lava cauldron to be a dangerous block, which can cause the player to end up in an endless death-respawn cycle. This can be reproduced using the /spawnpoint command, as well as using beds and respawn anchors.

Steps to reproduce 1:

1. /gamerule doImmediateRespawn true

2. Place the lava cauldron.
3. Set a spawnpoint in it using the /spawnpoint command.
4. Kill yourself.

Steps to reproduce 2:

1. Set your spawnpoint using a bed or respawn anchor.

2. /gamerule doImmediateRespawn true

3. /kill

4. Replace the block you are standing on with a lava cauldron.

5. /kill

Observed results:
The player respawns in a lava cauldron and quickly dies.

Expected results:
The player will not respawn in the lava cauldron, as it is a dangerous block.

Video:
0421 (1).mp4