I’ve been having heating issues at home with the arrival of cold weather. Our thermostat is set on 68 most of the time. I’d notice the temperature would be 66 or 65 and the heater would not be on. Turning off the heat at the thermostat and back on seemed to get it going. After a few weeks of this I decided to replace the thermostat.

This seemed to fix the issue and I praised myself for not having to pay for an expert to come out and do something simple for me. Until it started to not heat again a couple of weeks later.
Still determined not to pay someone big bucks I went to the greatest source of human knowledge and inspiration since God gave us the Bible, the Internet.
The main fan comes on right away, the heating element by the blowers lights up red hot then all three jets come on for about 4 seconds and promptly shut off.
It does this about 4 times and quits.
I noticed some led lights and they indicated low flame.
Googling this gave me some instructions on cleaning the flame sensor, a metal rod that sits in the midst of the flame and looks like this image:

The instructions were to remove this and clean it with sandpaper. Apparently it gets dirty and fails to register the flame is working properly. So far this appears to have fixed the problem.
We’ll see if I once again avoided having to have an expert come out charge me big bucks!
Beware: I am not a heating and air expert just a DIYer with Google. You have been warned.
Here’s a sample link of the advice I used to get mine working: