I'm not sure, but mine is doing it also and I think it sounds a little like what used to happen in the older cars with a coil heating up and not starting until it cools down. I think you need to take them off to get them tested, which I'm going to do. I may have my battery tested and see if something is not ruining it, because when I started having this problem I had to replace my battery and did fine for a while and then it started it up again.