Colt C50 dies off

Hello to all Mitsubishi experts, I drive a Mitsubishi Colt GLXi (C50) 1.5 l (C52A) EZ 10.1989 I have the following problem: When I was standing at the traffic lights by car (maybe 10 km before) the speed suddenly dropped to 0 and the engine died. After starting again the threshold rose normally to 1000-2000 revolutions and then immediately again to 0. This happened several times then until I could drive with gas a bit further around the car on the road. After about 1 -2 hours I was back at the car and then everything worked again as if nothing had been done before. The same thing happened to me exactly a month ago. In the meantime everything was normal. At that time I changed the spark plugs for new ones and hoped to have solved the problem with it. On another topic with about the same problem the holder was recommended in the Le Le I also did this and did not notice anything strange. In idle mode, the speed varies slightly between 1200 and 900 revolutions. What could be the cause of my problem? I am grateful for all the tips. Thank you very much in advance for your efforts! Sincerely, Joachim