Changing Safari Default Window Size

I'm running 15.4.1 and notice that I cannot adjust the window size of new windows in Safari. It used to be that whatever size the last window was, that would dictate the size of any new window. But NOW no matter what I do, each new window is super small. It's so annoying because I have to resize EVERY new window. This problem persists despite quitting and opening Safari, despite restarting the computer. I'm pretty sure this problem is coincidental with my installing the latest MacOS. I've looked through similar questions and found no solutions based on advice given. Thanks!