Is it normal that i get flashback memories of my parents having sex ?

Well the other day I was watching a french movie called Dans la maison(In the House -2012).

The story is about a boy named Claude who writes imaginary story about his friend Ralph and his mom Esther and Ralph's dad.

There is a scene in which,
Claude imagines Rapha's parents having sex; the scene is in the dimly lit bedroom so we get to see a brief glimpse of Esther's breast who is riding slowly astride Ralph's dad.

Claude stands there as Esther and her husband continues to make love , unaware of the presence of anyone behind them.

This dimly lit room , the suddenly brought back suppressed memories from my childhood. My parents and I were on a road trip (the trip that was supposed to help Mom get over the death of her father.)and we stopped at a motel at night for stay.

I was tired so I fell asleep instantly but I woke up at late hours of night on hearing the squeaking noise of the bed.

Like the scene from the movie mentioned above I see my mom riding astride my dad in a cowgirl position as my dad lay on the bed.

They were unaware that I was awake and I did not interrupt either (which would have been awkward for all).

My heart beat fast as I tried to shut my eyes tight and I tried to go back to sleep but all my efforts were in vain as they continued to "make the best of the road trip " the whole night.

There was also an instant during that night where I saw my mom parade naked across the room to get Cigarettes from my dad's trousers and light it and also collect a bottle of wine and two glasses on her way back to bed.

I had never seen my parents in that avatar before.

I was woken up late that morning (by my cheerful mom) for a late start to the road trip. I tried to forget and hoped it was a dream.

But it happened again on the way back from the road trip.