I have faced the same issue as soon as I have updated my Nokia 7 plus to Android Pie. Later, when I took it to the service centre along with the charger(which I got in the box). They tested by charging the phone with a different charger and cable combinations and it worked just fine with a different adaptor and the cable which I got in the box. So, the service centre guy said it was a problem with the adaptor. I have been using a third party fast charging adaptor since then & it's working just fine.
But, the catch here is I have tried charging my friend's Huawei P10 with my Nokia's charger and guess what... It's working without any issue.
I'm not able to understand clearly where the issue is... 樂
I have been facing the same issue after pie upgrade. However the delay is about 4-5 second
Issue is not with the adaptor nor with the handset.
Its something related to the pie upgrade.
Lets wait for someone's post with a possible solution.