Wifi disconnects when locked

I am having an issue with my iPhone 11. I have noticed that when locked for a certain amount of time when I tap on the screen to wake it up I see the WiFi had disconnected . It does however reconnect when I start using the phone. This hasn’t only happened on my home WiFi. I noticed it on a public WiFi as well. I have other apple devices and it’s not happening with them . My phone will be connected to WiFi when I place it down . When I wake it up I see the WiFi for a second then it switches to lte and then after a few seconds it shows WiFi again . I have read that WiFi will disconnect when the phone is asleep to save battery . I understand that but should I actually be able to see this WiFi lte WiFi back and forth when waking up the phone ? It doesn’t happen on my iPhone 7. I have tried resetting network settings and I even have erased the phone and set it up as a new phone without back up. Both things seem to resolve the issue but only for a day or so . Then it randomly starts to do it again. I have only had the phone for a few weeks . I am not sure if this is a software issue ( 13.3.1) or hardware issue . I am wondering if anyone else is having this issue and if they have managed to find anything that actually works to stop this ?