It's a server error. The official definition of the 503 status code is:
The server is currently unable to handle the request due to a temporary overloading or maintenance of the server.
It's the hosting server not having the resources to keep up with it's demand - unless Godaddy are doing maintenance on it every few minutes...
Godaddy is well known around here as not the greatest hosting company around, so unless you're stuck there I'd suggest exploring other options. (please don't ask for suggestions in here as that will get this thread shut down instantly)
For what it's worth, I've had them tell me straight out 'that's nothing to do with us' when I've been able to prove that it was, and it still didn't change their response.