Ignition errors / cracking when gasing

Hello, My Kia Sportage has the problem that he probably sometimes gives ignition errors and extreme jerkers with the gas. But these do not always occur. After a few days test time I would say if he was repeatedly driven only the short way to work (10 km), the error becomes more frequent and also worse. But once you have driven long distance, I have several days rest, even if after a few days only short and cold was driven. He shows no error. I find it very surprising that the error was so inconstant and therefore difficult to replicate. When it first noticed I was right in the workshop. Workshop staff sat there and got it along with it. However, since an appointment could only be made 3 weeks later and the error did not always come up, he said drive but as soon as an error is displayed, come directly. Problem now is, the ic h the Ruckler had at about 65% of the rides, but without error indication still, but at the workshop appointment the car naturally drives back and forth on the ride and when trying normal. Starting works quite normally the Ruckler arrive in gang 3-6. Workshop staff now does not know what it is exactly and can thus change nothing. Is this now a small or difficult error or the workshop not the most competent ? Let car always drive only briefly until the error will finally occur n my and workshop page of course difficult. I hope to thank you for your help