Motor Jumps on, but goes out again

Servus, this morning my wife calls and says that our Kangoo (bj. 98 1.4 75ps 165000 KM) starts but goes out again and again. She started working at 5 o’clock and has had to cool down at 10:00 hours. 5 hours the car has had to cool down. Early at 4:30 she has started normal. I can always make a long distance diagnosis bad, I need the thing in front of me. She was then picked up with our son and she just left the Kangoo. After work I am dangerous with my son. I have noticed that she runs as long as I keep my foot feeling on the gas. As soon as I leave my foot it goes off again. I decided to drive in a Renault workshop to ask what that can be. 2 traffic lights further she ran quite normal and did not go out. Temparatur I think. At the Renault they said as always “We have to connect it to the diagnosis device to see what is going on, costs 35 Teuros!” No tips or so Then I went to the car clinic to ask because they know each brand. They connected a diagnostic device and found no mistake. Cost: 0 Teuro! We think it has something to do with the Temparatur Geber. Has someone had something like that? Gruss Sean