In my case (DUDU7 3.5), Waze is in a PIP tile and a SIM card is installed. When waking up from standby, often (not always) the app shows a white map with not much response. The way to reset it is (as others have mentioned), open another PIP app (so Waze loses focus), open Waze from the app drawer, it opens as a black screen, then kill it via task manager. After that when going to the Waze PIP tile again, it restarts and all is good.
Also often when this happens (white Waze map), when trying to access the AC controls app via the floating button (touch assistant), it doesn't open at all. Going through the Car Settings app, then opening the AC app through there gives a result. It's as if the OS is busy after waking up from standby.
Doing a system restart fixes things in all cases.