Car falls down as it leaves line

[RPM5595]

I had a VERY similar problem a few years back. LONG story short, it was the battery. My battery was mounted lengthwise in the car at the front and apparently it had a cracked plate or two. When I would launch the plates would touch and ground out I suppose and the engine would flat die but then it would recover and run fine the rest of the run. Hope this helps.
Jay Roeder