Jumping Light-Point in the Sky

I like to report an incident, which occurred 30 years ago, somewhere in October/November 1978.
Together with a friend, we were traveling by car in the east part of France heading to Strasbourg. It was already night , might be 10PM or 11PM, 50-60 miles south of Strasbourg on a motorway and still we had to drive 1hour to our destination.  We have been tiered already , so we decided to stop on a park place for to take a little rest and to eat a snack.  It was a starlit night and while resting , we looked to the starry-sky.
After a while, we recognized that out of the star-scene in the west of the starry-sky a bright lighting star dissolved out from the star-alliance and started to move.  That light point ( approx. 30º above the horizon ), moved, even jumped very rapidly up and down, left and right, zigzag and perpendicular. e tried somehow to estimate/scale the magnitude of those movements by stretching or arm forward for to see how many fingers the movement ranged.  So far I remember, the movement from the light-point covered approx. the width of 2-3 fingers on a stretched arm, crossed in less than a second.
On the beginning from that "light-show" in the sky, we thought that an airplane or helicopter might be responsible for this , but we rejected this idea because:  1st  the movement started from a fixed-position and 2nd the profile of movements was so incredible, rapidly in speed and rapidly in changing of move-directions.
From our location we could not estimate how far away from us that light-point was , as according our first impression , that light-point appeared just as a bright star.
We could not hear any noise, either.
The light-point movements went on for some time and after a while we decided not to look further to that light-show in the sky and not to bother ourselves with things we cannot explain.
Somehow deep impressed and confused we left the scene and continued to drive towards to Strasbourg. We promised ourselves not tell anyone about that event , because we thought that nobody will believe us and we feared of ridicule.
However, 30 years past, but the memory on that night is for me still present  as it was yesterday.
I am reporting that case now, because internet does provide now the opportunity to share  those experiences with an open-minded community.  Maybe someone has a simple explanation for that .
Witness indicates that date is approximate.  PD