Symptoms of a bad/failing starter.

Starter

The starter is an electrical motor that uses power from the vehicle’s battery in order to start the engine.

Symptoms of a Bad or Failing Starter

Engine may not crank over when attempting to start the vehicle
Abnormal noise when starter is engaged

Starter Related Repair Advice

Many vehicles have a special ignition key that is electronically coded to start your vehicle. If the key or the system is having problems, the symptom may be the same as a faulty starter.
A weak or dead battery can exhibit the same symptoms as a faulty starter. The battery should be inspected and replaced as necessary before replacing the starter.
Corroded and/or loose battery terminals can exhibit the same symptoms as a faulty starter. They will need to be cleaned and possibly replaced before a failed starter can be properly diagnosed.
A faulty ignition switch may have the same symptoms as a defective starter
For vehicles with an automatic transmission, the neutral safety switch should be inspected. Manual transmission vehicles should have the clutch pedal switch checked.

 

Source (Repairpal).