The blower of my furnace makes a loud noise every time it starts. I understand that a large fan and the movement of large amounts of air will produce some noise. What I am puzzled by is the noise that sounds like a "starter." The noise only lasts for about a second or two; then there is just the expected sound of blowing air. 

Could it be a motor failure problem at its infancy, or could it be related to the capacitor start on the motor? The blower pushes air without a hitch. Is this a normal condition that is heard on all blower motors?

Additional details:

My system is a direct drive motor driven, "squirrel cage" type fan, hot air, oil fired furnace. I am aware of the sounds of the fuel pump and then ignition of oil rumbling in the fire box (I don't know if that's the right term) but anyway the sound that I am trying to troubleshoot is the noise when the fan motor starts (my best description is that of a car starter) It may be spelled RRen-nen-nen-nen and then just the sound of moving air after the fan gets to full speed. There is a capacitor on the motor, could it be a malfunctioning capacitor? I have lived in an apartment building for 30 years and now in a single family dwelling, and have never heard any heating system noises. My concern is in what to replace; motor & capacitor, or just motor, or just capacitor or is that just a noise that I am going to have to get used to?