Delayed Notifications on cell data

In my iPhone 13 iOS 15.4.1, notifications are 4-8 minutes delayed. When it is connected to wifi notifications works perfectly. But in cellular data there is a problem. I have a stable cellular internet data connection. When I am using an app which uses my cellular internet, app works completely fine but notifications are delayed. Background app refresh is on. Also restarted my iPhone still getting same issue. iPhone is not in low power mode and in cellular data settings low data usage an roaming is off. So, please recommend me a suitable solution. Is anyone else facing this issue?