Very common. We see at least 2-3 everyday in A&E.
Typically, happen in children 6months -6 years, with fever, all 4 limbs jerking (Generalized tonic clonic), less than 5 minutes, wake up within an hour. No subsequent weakness or long term effects. Slightly increased risk of developing Epilepsy. No investigation or treatment required.
If any deviation from the above, ie Atypical feature, investigation may be needed if happen more than once.