No Internet Access after restarting System in Ubuntu 18.04.2 LTS

I am facing one problem with my system having Ubuntu 18.04.2 LTS (recently upgraded). Problem is Wifi is working but No Internet Access, I tried with

nameserver 8.8.8.8  nameserver 8.8.4.4 

but after restarting the system these two lines are disabled automatically.

Please help me to resolve the problem Thank you so much