I have a 2000 S40 and I've been having a problem two volvo shops can't figure out. My car will start after sitting for long periods of time (overnight is a good example) but if I drive it down to the store or something, when I come back out, it won't start. If I wait up to an hour it will start. There is electrical power as the lights come on, antenna goes up, radio is fine but there is no click or anything to hear it even try and start. No service codes are registered. Battery is brand new and I have to play the part swap trying game because that is pretty expensive in this car. Help?! If there is a mechanic local to 02184, contact me!

 

I would start by checking for power at the small trigger wire at the starter when it won't start. If you have power to the wire and it doesn't turn the motor over the starter is bad.
But if you don't have power then I would look at the PNP switch.