Heat kicks on at Random- HELP

I have a ranch style house and I am a first time homeowner. The house is less than a year old (yes I have a builders warranty) and use gas for the furnace. The issue that I am having is that the heat kicks on a random times. For example, I could have the heat set to 70 but I will wake up and it will be 60 inside the house. The a/c and fan work with no problem so its just the heat. The heat does come on, but basically whenever it wants to. At first I thought the thermostat was the problem so I changed it out for a Google Nest. When I did the initial test with the Nest, the fan and a/c came on almost instantly, but the heat took at least 20 minutes to come on. I know that the builder will come out to fix it, but since I don't know much about these systems, I would like to do some basic troubleshooting before I have him come out. This has been happening since the very start of winter (the first time ive used the heat).
Troubleshooting I have done:
-Turned breaker on and off
-Changed thermostat (originally a honeywell)
-Turned off schedules on original and new thermostat

source https://hvac-talk.com/vbb/threads/2227240-Heat-kicks-on-at-Random-HELP?goto=newpost