Clean connections, Make sure you have a good ground. Charge battery, I like to do that overnight. Good system and a charged battery will have 14.5 Volts at the battery. A weak battery will need constant charge and will have trouble starting. If the start issue continues, get the battery tested, under a load. Most parts houses can do it for free. If the starter works, it is good. If it makes a lot of noise you might want to take a good look at it. Only a few bolts and wires to remove it so that is easy to do. A note, remove the cables from that battery first.
