Here is a service manual
http://www.servicematters.com/d...0Sheet%20-%208528192.pdf

sometimes this dryer works fine. next time you set everything and push
the start button and nothing happens, other times it can be running and
stop in the middle of the cycle and cant get it restarted. then you push
the start button it might start and it might not. the door switch seems to be fine.

Sounds like you may have a loose connection somewhere.
I would unplug it and check the connections at the unit's terminal strip.

When it will not start try wiggling the plug at the wall receptacle could be a loose connection at the receptacle or in the plug itself.

The stopping mid cycle sounds like it could be the motor overheating and tripping it's internal thermal protect. You then have to wait for the motor to cool down before restarting. But this does not explain why it will not start when cold, usually the motor will buzz if it has problems starting when cold.