Wild Magic Surge:
Starting when you choose this origin at 1st level, your spellcasting can unleash surges of untamed magic. Immediately after you cast a sorcerer spell of 1st level or higher, the DM can have you roll a d20. If you roll a 1, roll on the Wild Magic Surge table to create a random magical effect. A Wild Magic Surge can happen once per turn.
If a Wild Magic effect is a spell, it’s too wild to be affected by Metamagic. If it normally requires concentration, it doesn’t require concentration in this case; the spell lasts for its full duration.
What fulfills the requirements of a "sorcerer spell of 1st level or higher"?
A few options that I can think of for defining a "sorcerer spell"
Any spell that you’ve learned from Sorcerer and that you’re casting through the Spellcasting feature.
This is my idea of the default answer. A sorcerer spell is a spell you’ve learned as a sorcerer and are casting as a sorcerer.
Any spell that you’ve learned from Sorcerer
This is also reasonable. But it opens the door to casting spells through magic items, such as Cape of the Mountebank, triggering wild magic surges.
Any spell on the Sorcerer spell list.
Still reasonable. This would mean that learning the spell Hold Person through Bard’s learned spells and casting it could trigger a wild magic surge, as it’s a spell that’s both on the Bard’s spell list and the Sorcerer’s.