Spontaneous Combustion (3.5e Trait)
From D&D Wiki
Your uncanny ability to light yourself on fire has followed you throughout your life.
Prerequisite: Character must be able to cast magic.
Benefit: The character gains a 1d4 of extra damage while using any kind of fire spell/magic.
Drawback: You have a 1d8 chance of lighting you, and characters in a 5 foot radius around you (friend or foe) on fire for a 1d4 of turns while casting any elemental magics.
Roleplaying Ideas: You never fully gained control over you're fire elements, however they were always your most powerful.