Carrier heater on heat and air unit turns off after 4 minutes before the house is warmed. And then off and on in short bursts thereafter The house gets warm eventually the heater is always doing this.
This was a new house with a new unit two years ago and has been like this since moving in and two service people looked at it and said they didn't know what was wrong
.. anyone know what to do about this
Is it possible the thermostat doesn't work. The air conditioner works fine and when it comes on it stays on till the house is cool and only takes about 10 minutes

I would start by removing the thermostat from the heat circuit and wire direct. This way the thermostat will be removed from the situation and if the thermostat is causing the problem you will know. You might also check the internal setting for heat anticipation or longer run time if it is a digital thermostat.

If non of the above makes a difference then the controls especially high limit and fan control will need to be checked among other items.

I am surprised no contractor you called could fix the situation.

What model Carrier? High efficiency? Plastic Pipes? Error codes?