Have to keep turning the key back and forward several times before it will finally start.

Could be the key switch, or the starter, or another component.
You would need to check for power at the starter terminals when the key is in the start position.

I love my Rangers, and it sounds like you need a new starter drive, better know as the bendix. It is cheaper to buy a new starter. As far as the door locks, I would get the starter fixed first and the door lock problem may go away. sounds like the starter is dragging the power down and could cause a number of strange thing to happen. Hope I have help you solve your problem. I think It will.

Starter going out. Also check battery, Make sure it is still charger/holding charge.

You should be able to reset it without the radio. Turn your key forward 2 clicks until right before the car would normally start, leave like this for ten minutes. (No less than ten. Eleven is safe) Turn the key back to the "off" position for 5 seconds and repeat the whole process 2 more times.

So that's forward 10 minutes, back for 5 seconds. Forward 10, back 5. And the final forward 10, back 5. Try to start vehicle.

This is a complete GM Passlock relearn. Should take about 30 minutes. If that doesn't work, you may have something broken. Normally, the passlock doesn't get triggered for no reason. So worst case scenario, you can always bypass the entire system. Here is a great link with a ton of info on Passlock and how to get around it

http://vatspasslockpasskeysecurityhelp.yolasite.com/

These vehicles have a built in antitheft system. When switching the ignition you interrupt this system. You will need to do a system relearn after the new ignition is installed. It will not start until the new ignition is installed and relearned. Step one. Put key in ignition, turn forward 2 clicks until right before it should start. Keep like that for ten minutes, NO LESS. Step two. After the ten minutes, turn key back to off position for 5 seconds. You need to do steps 1 & 2 a total of three times in a row without trying to start the car in between. The whole process should take roughly 30 minutes. After the last time waiting 5 seconds in off position, turn key forward and attempt to start the vehicle. Remember no less than ten minutes when forward, maybe do ten minutes and 15 seconds to be sure, some people even do 11 minutes.

Dieing while driving but restarting right away, no starts from a dead stop. To me this sounds like the anti theft security system shutting you down. These have been known to turn off injectors while driving and starters while stopped. Check and see if a light is illuminated that says SECURITY when it fails to start. Leave the key forward and look for it. If you see that light, then it is 100% the security system. This link has tons of info on symptoms, causes, and some DO IT YOURSELF solutions. http://vatspasslockpasskeysecurityhelp.yolasite.com/

Could be your starter, sounds like your starter soloinoid(pulls starter gear into flywheel) might be defective. First it will not pull gear in, then if it sticks in your car could keep starting even if the key was turned off .
without looking at the car I could'nt say how hard it would be to change. It has been my observation that newer cars are much more difficult to change

if you turned the steering wheel after shutting off the engine and the steering wheel caught the lock and tried to turn back it would hold pressure against the ignition lock cylinder. if it happens again try pulling the steering wheel hard one way or the other and turn the key at the same time.

yes, there is a shiftlock sensor, so you can only take the key out when in park.
Getting at it requires removal of the center console.
When you have it in park - give it a little tap forward before turning off the vehicle.

It may be the shifter interlock switch - jiggle the shifter into and out of Park.
It may also be the Ground/neg battery cable - they corrode at the fenderwell every 2-3 years. Remove from battery and fenderwell, bruch off white powdery corrosion. Reinstall.