I have a 97 accent manual shift. About once a month the car won't start. I crank it, but it won't turn over. I don't have my foot on the gas pedal. If I walk away and return in 10 or 15 minutes, it usually will start, but sometimes it won't so i have to tow it. The starter, plugs, filters, battery etc are all fine. The car starts almost all the time, but for no particular reason it occasionally won't. It seems to happen when the heat and humidity are high, but I've also had the problem first thing on a 40 degree morning. Any ideas would be greatly appreciated.