Thanks. That's just not right.
There are a lot of notorious memory hogs, but that's no excuse. 16 GB should be more than a comfortable amount even for them. By way of explanation, the dialog box alleging running out of application memory can also occur if the virtual memory swap file (stored on the startup device — 25+ GB in your case) has grown large, leaving it with little available space. Might that be related? If so you need to find a way to reclaim additional space: Free up storage space on your Mac - Apple Support.
I suspect you will not find those explanations satisfactory. Consider using EtreCheck, and posting its report in a reply to this Discussion. Instructions and a download link are here: How to use the Add Text Feature When Posting Large Amounts of Text, i.e. an Etrecheck Report - Apple Community. It may or may not reveal some actionable information, but the program itself is small, does not require an installation procedure, and it does exactly nothing unless it is actively running. You can simply drag it to the Trash when you're finished with it.