Compressor turns on but blower motor in furnace won't engage. Appears to have power and wants to turn over, rotates slightly but then stops and makes a thumping sound. Any suggestions?

Is possible you might have a bad capicitor,when its trying to start try spinning fan manually ,if it starts and runs you need to replace capicitor with an exact match. They are cheap if you replace and still doesn`t start u not out much, under 10 bucks

If the capacitor doesn't fix it then ohm the motor out.