With fully charged battery, I can start the car up and drive around for a while. However, once I park it for a bit, when I try to start it up again the battery will have drained a bit and when I turn the key the volts just drop and I have to be jumped. Battery is good, alternator is good, I'm a bit lost. Just started doing it out of the blue, no changes made where a screw-up was possible. Maybe a bad ground somewhere (where?), bad starter? Any suggestions are greatly appreciated.

One other problem, my left rear speaker is not working. The yellow wire w/ green stripe is getting no power to it. I haven't yet been able to find where the power is lost, any suggestions of connectors to check, etc?

I hate wiring, I like the easy "bolt this part here" stuff