The short answer is no. Auto-fill on page load is a feature included in Bitwarden’s browser extensions that is turned off by default. Although it is typically safe, this feature is not enabled by default due to the risk of compromised or untrusted websites using it to obtain login information.
Unless you deliberately change the settings to enable the ‘auto-fill on page load’ function, this is not something you need to worry about. And it comes with a visible warning, telling you that it is off because it can be potentially dangerous.
Bitwarden has also taken some additional steps to ensure users’ safety by only filling iframes from trusted websites. If users manually auto-fill an untrusted iframe, Bitwarden will display an alert that will give them the option to either cancel or proceed.