They often have a safety cut-out switch to stop the machine if the motor gets too hot - obviously this switch is mounted on or close to the motor itself.
I am unaware of the need to have any other switch other than for on/off.
Your machine's overheat switch may have operated and not reset itself - but I doubt it...
The most common fault with vacuum cleaners is a broken conductor inside the power cord - where the cord bends at the plug or where it bends going into the machine - enthusiastic tugging over an extended period is the cause.
Try cutting six inches or so off the power cord and fitting a new plug - this has fixed 75% of the cleaners I've repaired.
Good luck...
Peccavi, November 2012
