Modern Vespa

I was initially worried about how the temperature would affect the PX, but was surprised to have her run as usual and maintain 60 mph on the highway. Everything was great until we were about 5 miles away from Las Vegas. I heard this really weird, feint sound (I barely heard it over the wind) - it sounded like there were a couple nuts (or metal of the like) loose somewhere in the body and they were rattling around due to the vibration. However it was coming from the engine (I think). I put up my visor and ducked behind my windshield to try and really hear the sound and isolate it - at that moment, my gf noticed a puff of smoke coming out my exhaust. I was about to pull over when she said it stopped - so I kept going. I rode very carefully from that point - my number one concern was a seize of the engine, so I had my hand on the clutch just in case. Zoomed for a couple more minutes without any issues (and no smoke) but still heard the noise (again, very faintly), then boom - my engine turns off and I have no power. I immediately grab the clutch and I coast to the emergency lane. I take a second to collect myself, and try to restart it - the PX fires right up and I carefully get back on the highway. This happened a total of 2 more times before the traffic slowed (construction) and we exited - from that point had no problems.