Photos loads and flashes when iphone connected

Since downloading the new OS (10.15.7) anytime I connect my iPhone via usb to my iMac for charging, Photos opens and immediately toggles between my photo library and a white screen informing me that it is "preparing to import" from the iPhone. No import happens, and even if I close Photos (even with a force quit) Photos immediately reopens and starts the sequence again. Thoughts? Fixes? This has only started with Catalina

Thanks