I have a 2008 Jetta that refuses to start every now and then. When I turn the key it makes clicking noise like battery is dead. I had the battery, starter and alternator checked. All good. The car starts back up usually after 30 min to an hour. Today I pushed gas pedal while trying to crank it and it eventually caught. There are no check lights. Car runs fine when starts. I have no idea what issue could be because it starts up most times. Please give me advice. Thanks so much.
The problem probably resides in a connection somewhere in your starting system. I would start by disconnecting at the battery, making sure all connections are clean, then re-securing them so they are good and tight. Move your way back on the cables to ensure all other connections are good in the same manner. While you are moving down the cables, ensure there aren't any "fat" spots. This is a sign of corrosion inside the cable and can cause starting/charging issues. Also, ensure your grounds are good and solid. Since you stated the battery, starter, and alternator are good, the wiring is the only thing left which might be causing this.
EDIT: Also, it is never good to press the gas pedal on a fuel injected car when trying to start it. First of all, it will do you no good. When cars were carbureted, you would press the pedal to get some gas into the intake via the accelerator pump. It doesn't work that way with fuel injected cars. Secondly, most manufacturers use the throttle when starting to do a throttle position reset. If you are tromping on the pedal, it might cause this to reset, which will cause you even more problems.
Your vehicles problems lies with the starting circuit. Battery, starter motor and solonoid, cables, power and earth points. A test on the system which is gaining prominance is with a battery/starting testing tool called here in the UK by the name of Midtronics. A fracture internally of the battery can be diagnosed. Some of the cables can be spliced internally in their loom and these will require special attention for continuity. Your problem will mean a series of tests and may be best carried out by an auto-electrician.