Seemed to happen during playing, after died twice in quick succession, once via being pushed into lava by a hoglin in the nether, and then when tried to go back through the portal to get my items, was attacked by piglins and thrown from a great height into lava below.

After respawn, seemed to be covered in flames and it didn't seem to disappear. No sound or damage, just the flame affect on the screen. 

Then tried to "dunk" myself in water to see if it would clear the effect, and it didn't seem to work.