I have 35,000 BTU wall furnace with a blower motor. When the furnace heats up, the blower starts for about 2 or 3 seconds, turns off for about 5 seconds, then back on for 5 or 6 seconds, then off for 5 or 6 and then back on as it should (stays on). Shuts off appropriately as it is controlled with thermostat. I am trying to figure out why it hesitates to start at the beginning. I have oiled the motor- it spins freely and makes no noise.
I doubt this is a motor problem. Sounds more like a thermostat problem, but not the main heater thermostat. The fan has its own control which, according to the manual, starts the fan 5 to 10 minutes after the furnace starts and then it runs until 5 to 10 minutes after the furnace stops. My hunch is that it is temperature-controlled and is cycling too fast at the beginning - i.e., it blows for 2 seconds, which cools down the initial air flow so fast that it turns itself off, then starts again after another 5 seconds, etc. until it runs continuously.
If it has always been this way, contact the manufacturer.
If it used to work correctly and recently started having this problem, a good cleaning may help.
By the way, I find it interesting that the blower kit is optional. 35,000 BTU is quite a bit of heat to generate without a blower. So I would definitely want that fan running well to circulate the heated air.