All vacuums generate heat and some have automatic cut off switches when the vacuum does overheat. When this happens the manufacturer does not want you to just turn it back on, they want you to know there was a problem and to let it cool down. They often do this with a restart button. Having to press a restart button is supposed to make you think a bit more about the problem and, perhaps, let the motor cool down before restarting the vacuum. The button is often small and red.