I have a Bryant heating unit that is 8 years old. The blower will run and cut off intermittently 3 to 4 times before the heat will come on. This condition will last for
3 to 4 cycles until the heat will disperse. It will run for awhile and then start cycling on and of until cold air will be dispersed.

Thank You,
Stanley

The filter for my Bryant is a green washable "3M" pad material, located behind both the outer panel and the inner panel, lying flat, near the bottom of the inner door, which is about half way off the floor.
It should be washed and dried once a year.
If not --- you are wasting a lot of fuel!
You can easily google the model number and print out the whole manual.