Micra K12 sometimes goes out

Hello! I have a problem with my NISSAN Micra K12 (year 2003, running almost 90,000 km). If I am standing at the traffic light, for example, the rev indicator is sagging off (it does not run) and it has happened to me a few times that, if I drive e.g. into a roundabout or at a junction/traffic light, switch down and slow down that I have run out of the car. He jumped up to now always immediately, but a nice feeling is not. I was already in the NISSAN workshop to the F I was told to wait for a control person to approach. I was still in a free workshop and got a similar statement. It could be “a barrel without a floor”. Does anyone have an idea? Thank you in advance.