[mr0077]

Curtis, Bill could be right...other starter-related causes:
hot starter - find (or make) a heat shield
dragging starter - not too likely, but a possibility...get it tested
power cables too small (particularly with trunk-mounted battery)
bad electrical connections - easy to check
You can check the last two by hooking up jumper cables in parallel from the positive cable to the starter, and from the motor to the neg terminal. If it works better, remove one, try it, reconnect and remove the other, try it...this will tell you if one or the other cable needs a little help (bigger size), or if there is a bad connection.