Is it normal to start having regular strong contractions (1 hour apart) and then suddenly stop after 6 hours?

Yes, I experienced this during my first pregnancy. I had 30mins contraction intervals for about few hours and I went into labor ward and strapped onto contraction checking machine and there was no regular contraction and I was sent back to home. My real labor came 1 week after that. Thus, for my 2nd pregnancy, I tried to monitor closely and record the contraction intervals down using mobile apps. You can download 'contraction timer/tracker'. The apps helped me to plot a chart whether my contraction intervals getting closer and regular.