It sounds like you could have a pressure switch problem. It does not from your post sound like a constant one. When the furnace goes out, if you put a jumper wire across the two wires of the pressure switch it should fire right back up. If the little fan (inducer assembly) is making alot of noise or vibrating, this is going to be the more likely problem than the pressure switch.
unit does not have a pressure switch..........its natural draft