During the night the heat in my HVAC stopped working.
I switched it to air and turned down the thermostat and the AC kicked on, I switch it back to heat and nothing, tired "auto" and "fan" settings.
It was working fine when I went to bed, heating fine, kicking on and off just fine, then nothing.

I would suspect either the thermocouple or the "Hot Surface Ignitor" (HSI) have failed.

You'll have one or the other, depending mostly on the age of your furnace. If it is 20 or more years old, you'll have a pilot light with a thermocouple. If it is newer, you'll probably have a HSI.

Both are pretty easy to replace. Once you see them, you should be able to see what to do. If not, let us know.

Best of luck,
WallyH

Exact model and brand name?