I am having trouble with my heater. It kicks on, the burners are lit and the motor is on, but no air comes out the vents. Why is that?

Sounds like the blower motor isn`t blowing,, have you checked/or replaced the filter?, is the return air vent closed off?, most furnaces now-a-days have 2 motors,, if the exhast/venting motor isn`t working it won`t start or light the burners

Gas ignites,heats up but no blower then turns off