furnace not keeping up

It seems that my furnace is not kicking on when I think it should, it is colder in here than I have it set. I seem to be able to "jump start" it by turning the emergency switch off and then on. At that point, the furnace will turn on and do its thing - blow air for about 3-5 min or so, then turn off. I wait for it to kick back on to continue heating, but most of the time it doesnt and I need to repeat the above. What could be causing this?

What type of furnace? I assume you have a heat pump because you mentioned emergency heat, but more details would help. Things like age, model number, size, etc. can also be useful. If it is a heat pump, is there also a gas furnace as well?