Outside temp is 45 degrees.

I have an American Standard electric heat pump system. When I turn the heat on and set a desired temperature it never reaches that temperature before shutting off. It will blow warm air for 15 minutes and then turn off. I have to shut the t-stat to OFF and wait about 5 minutes before switching it back on to HEAT to get the air to start blowing again. There is warm air blowing from the vents so I'm not sure what the issue is. It just seems that the air is not being regulated properly.