Why does my e-bike motor cut out for a second while riding, then come back?

A common cause is a brake lever that doesn't spring fully back. Each lever has a sensor that cuts the motor when the brake is pulled, so a lever that stays partly pulled keeps the motor cutting out. Check both levers by pulling and releasing them to see whether they snap back fully. A lever bent slightly by a fall can rub and cause this, and a service center can straighten or swap it. Also check that the battery is seated and locked, since a loose battery can cut power. Motor cutting out on hills when the battery is low is normal.