What does it look like when a baby has a seizure?

Shaking. There are several types of seizures in babies. In infants, seizures appear in subtle ways, like lips smacking, eye twitching, and tongue thrusting. Older children can have generalized seizures, with whole body shaking and stiffening, or partial seizures, with just one side of the body shaking or twitching. Some seizures can appear as staring spells, or as episodes of uncontrollable movements.
Rhythmic shaking. Seizure's usually present with rhythmic shaking of the limbs. They're often symmetrical (both arms or legs) and the infant is not usually alert and smiling during the seizure. After the seizure, the infant is usually drowsy. Seizures are not common, but if you're unsure, call your doctor. If you see a type of movement that happens repeatedly, videotape it so your physician can see it as well.
Varied. The appearance of a seizure can take various forms particularly in the infant. The baby may go limp(atonic) or tighten up and and alternatively flex and relax its extremities(tonic clonic). Seizures in the immature nervous system can be very subtle such as a grimace or episodes of pallor.
Many different types. There are many different types of seizures that occur in babys. speak to your pediatrician about your concerns.