2000 Kia Sportage - won't start - P0560

Check the park neutral switch for correded wires and terminals also check the conectors just below the battery, they often corrode.
One other direction to go is if you have an alarm system. Disconnect it completely(remove it physically from vehicle) and go from there. Often these systems interupt current intermittently (even if they are "turned off" they still have the vehicles current passing through their circuitry to operate the vehicle. Did you find out what the code is?

Do a charging stsem test only after running the vevicle for a half hour or more (to make sure it is well warmed up) if nothing shows up then take a look at the underneath of the fuse box located at the driver's side of the engine compartment. They had a tendancy to corrode near the main wires and under the fuses and relays.
You may also want to check if the "main" relay in there is also put in correctly(I've found them reversed often!)
Goodluck!

Ok so all the basics were covered. Now!
I looked into your "general loss of power code 560" and it turns out that it isn't! In fact its a very specific code : its loss of power to the ECM or internal ECM failure!
In other words check all the connectors at the computer and associated grounds and if you see nothing loose or corroded then wait till the problem acts up and hit the Ecm(computer). It should be located at the floor/firewall on the passenger side of the vehicle (inside)
By the way the ECM is covered for 7 years and I forget how much mileage because of an emissions issue with the government regulations! Please note this area is VERY SENSATIVE to the slightest deviation of even one terminal or pin connector
By the way just out of curiosity what part of the country are you wrining from?(Don't have to be specific. State or province will satisfy my curiosity?
Good luck this sounds like the kind of problems Ilike to find! (Yeah I'm a weird one.)