If you have the car ventilation blowing on the cigar that may make a difference too. I've noticed that when I take a walk with a cigar, the burn will often get squirrely. I usually smoke on my front porch. I can smoke a cigar about half way down and it will burn just fine. Then I'll put my dog on a leash and walk around the block and the cigar will start to tunnel or canoe. It may be that I'll start puffing faster (or slower) in response to my walking, so that may affect it too.
BTW, my dog shows a good Pavlovian response now. Whenever she smells a cigar, she goes ballistic, because going on walks is her very favorite thing.