Suggest the following: 1) Check integrity of positive and ground connections from battery to the starter. You could have loose cable or corrosion. 2) Stop by Sears Auto Center or Interstate Battery store and get your battery checked. If you've got original battery it's not unexpected that it may be on its way out. I live in N Central Texas, and I've had several 3-4 year old car batteries crump with little or no warning.