Q: Car won't turn over

This may potentially be a faulty starter solenoid or relay depending on the symptoms. The starter solenoid is located on the starter and has internal electrical contacts that transmit electricity to the starter. When this fails, it may cause a clicking sound and will not allow the starter to engage the flywheel when you turn the key. The starter relay directs power from the battery to the starter solenoid which then engages the starter when you turn the key. When this is not working properly, you may notice intermittent starting problems as you describe. Generally, when this does fail, it does so very randomly and usually without warning other than intermittent starting. The power from the battery will still power other accessories such as radio, horn, etc., but you may not have any power to the starter. I would suggest having a professional from YourMechanic come to your home to diagnose your starter.