Sensation of loud noise, crash, and time stopping

This is not an account of seeing a UFO, but of something that occurred that is just as peculiar.  
When I was a young child, my family was driving down Hwy 49 S in MS towards the Gulf Coast.  About two hours into the trip, I heard a loud noise and had the sensation that we were being hit by a semi-truck.  At that point, time seemed to stop.  However, there was actually no "real" noise that I know of, and we were not in an accident, as I had felt.  
As soon as I felt things return to normal, everyone in the car (there were five of us) turned to each other and asked "what just happened?".  Everyone in the car had felt the same thing I had.  
I remember my parents were somewhat concerned about feeling like time had stopped and immediately checked the clock, but it was the time it should have been.  
Can anyone give an explanation for what could cause this sensation?  It has been a long time, but it still perplexes me.  It would be nice to finally have a reason behind this phenomen.
Witness elects to remain anonymous.  PD