After opening a few browser windows Edge stops and won't let me open more until I stop/start edge.

Should clear the browser data and cached files. This will free up some space and remove any corrupted or outdated files. Next, you should close other tabs, extensions, and apps that you don't need. They might be slowing down your browser or causing conflicts. Then, you should make sure Edge is up to date. You can check for updates in the settings menu. Sometimes, updates can fix bugs or improve performance. Another thing you should do is verify that third-party security software is up to date and scan the device for malware. Malware can interfere with your browser or compromise your security. You can use Windows Defender or any other antivirus program you trust. Finally, you can try changing the default app for URL to ‘Internet Browser’ instead of Edge, then set Edge as the web browser again. This might reset some settings that are causing problems. If none of these steps work, you can also try resetting the settings to their default values in the settings menu. This will erase any customizations you made, but it might also solve some issues. Hope this helps!