s 10 notification delay

First do you have this issue while being contacted to phone data or wifi ? second check your device care app if those applications are of sleep mode

This can happen if your device is in power saver mode, background data turned off, or because of battery optimization settings. Check these settings one by one.
Also if the app is restricted to run in background it will not show notification until you open it.

Hey there, it's an Android Pie bug itself. it has nothing to do with the device, I've used 3 phones after updating to pie and it all has notification delays or suddenly all the notifications come together even though we opened them a while back.

I face the same issue at some times