chrysler neon

i have a 200 chrysler neon lx and the heaters do not work they will blow a bit of hot air for a couple of seconds but as soon as i start driving it just blows cold air also the fan kicks in every couple of mins when the car is idel and in park havent noticed if it does it when im driveing dont no if the two are connected if anyone can help please reaply to this many thanks