I'm not much of an electrician, I don't know if it has a thermal or overload protection shut off or not, the new tools coming out have so much going on inside them today.
Usually the type of action your getting sounds like there may be a loose wire between the trigger and motor. When it shuts off try turning the unit over and around while gently shaking it. If it intermittently jerks on and off its a loose or disconnected wire. If it doesn't try to turn on when flopping it around try a more aggressive shaking while rolling it about.
Still nothing then it could be some kind of overload protection and may be due to a ground. The shut off may need to sit for a while unplugged, if so come back in 10 or so minutes to see if it'll start once plugged in cold. in any case even if it does take it back for a replacement. At least then you can speak with authority
Work smart not hard!
Never bite the hand that looks dirty