Iphone 12 Pro Max not loading apps/pages when waken up.

Hi, Since receiving my 12 Pro Max from Apple in late November I've been having problems loading apps and webpages when I wake up the phone. Turning off and back on wifi on the phone solves the problem. But after a while I get the same thing again. I've tried everything apple support told me to do including setting the phone as new, without any apps. After chatting and speaking numerous times with apple support they were of no help. I also tried every tip and trick I found on the internet and nothing solved the problem. So i decided to return the phone and get another 12 Pro Max from Apple. Got it yesterday and surprise!, I have the exact same problem with this one too!. I'm concluding that the problem is my wifi and not the phone as non of this happens with my XS Max or Ipad Pro. I have a combination router/modem from my cable company, it's called connect box.

Any help or suggestions will be greatly appreciated.

I don't want to have to return this one too and keep using the XS Max :-(

Thanks,

WJ