Sounds like faulty ignition switch or loose connection on ignition switch or first connector block. Your bikes only three months old have the dealer put it right.
...that was the absolute first symptom I had with my '07 when my ignition first let me know it was ill. However, I was in 4th going into 5th when it happened, although, it came back to life before I had a chance to pull over. It only did that once. Then came the, "Hey, my lights won't turn off", followed by the game of "mystery start", when I was never sure if it was going to start. Triumph replaced all locks under warranty.