maybe it was the gas engine kicking in? the CT can run up to 45mph on electric if it's a coasting type drive with minimal acceleration. but of course the gas engine kicks in if the battery is low or if it senses you need a little more juice (i.e., on an incline).
my experience though is that the hybrid system is extremely seamless and invisible. i can't recall what i thought of it when i first got it, but almost three years later i don't feel the gas engine come on. and even if i do, it's not really a "surge".
perhaps the salesperson had it on sport, in which case the pedal response is much faster and will be a little jumpier.