Hi, We have a Lennox oil furnace. We use it to suppliment wood heat and in spring and fall when we need a little heat but it's too warm for a fire.

Yesterday it started rumbling and vibrating when the furnace first comes on for about 20 seconds, then it gets much quieter, but is still a little louder than normal for another 20-30 seconds. After that it runs normally, puts out heat like normal.

Is there something we could do ourselves to fix the problem?