I come home my house is cold, Frequently. OIL furnace. I go to furnace switch main switch off and back to on. Furnace fires and fire goes almost minute and shuts off. If I bump the furnace or tap the primary control the furnace starts fire and runs. Not always though. Soometimes have to use switch twice and tap the primary some more. Also the furnace fire goes for like three hours to raise room temp from 54-56deg to 69deg where thermostat is set. Called Honeywell tech. They guided me through troubleshooting They say trouble on furnace side not stat.
Whet might be going on?

Start checking the furnace wiring for any loose wires. Burner,controls, etc.