it's difficult to diagnose over the internet, but it would seem a check of the battery and charging system would be the first thing to do. You may need to replace the battery, then possibly the voltage regulators on the alternator. NAPA has some good shops for checking out electrical systems if you aren't confident in doing it yourself. There must be good solid power from the battery to spin a starter. If those check out, then move on to checking the starter. Bosch is the brand to buy for starters.