Since the Gf is opening I suspect a short. Except that when you reset it, it
doesn't click off again? Does it even hum or anything? If it's a two stage
motor could be the starting circuit. If it clicks off when you plug it in with
the switch OFF, you may be lucky, and the short is between the plug and the
switch. A short short. Maybe you over twisted the power cord or ran over it.
Get out your ohm meter or test light and check for shorts. WITH THE MACHINE
UNPLUGGED!!!! Check it with switch on and off, Gf on off, from each prong to
the motor housing, to the frame,every kind of combination you can think of.
Since it's new there may be a loose screw or connection so I might even take
off any cover over the connections, but I wouldn't get involved in opening
the motor to check the starting circuit or commutator. Just commute with it
back to where you got it. If it was only summer time I would commute over to
the park and check for short shorts myself.