I recently built my first drone and after flying it for the first time everything was working well. I did crash it once but everything still worked afterwards. However, when I went to fly for the second time one of the motors didn't spin properly when armed. It would jitter back and forth and occasionally spin a couple of revolutions but always stop completely after a few seconds. All the other motors spin with no problems. I'm quite new to this and can't spot anything that's wrong. Any help would be greatly appreciated.

I'd swap the motor that's twitching with one of the others that isn't. If the twitch follows the motor, it's probably the motor. If the twitch stays in the same location, it's probably the flight controller.

It was the motor. Swapped it with one of the others and it kept having problems. Thanks for the help.

Check the motor, wire and connector (if it has one) over for any repairable issues. It never hurts to have a spare motor.

So it mechanically feels normal when turned by hand power off?

The prop was not free enough to skid?

Also check the motor screws aren't too long and touching the windings. If it is you may use a slightly shorter screw or 'Dremel' grind a little off then re-insert, hopefully it hasn't damaged the windings. Another thing to check is it may have picked up something and is in between the magnets and stator.