I own a fourplex, which I own as an individual. Should I change transfer ownership into a LLC to reduce liability?

I assume that you do not live in the fourplex. Yes, you can transfer the property to an LLC to limit your liability.  That would shield your personal assets and any other business assets. You can request that your lender approve a transfer to your LLC.  However, many of my clients get the financing in their personal name and then transfer the property to an LLC that they own and it hasn't triggered enforcement by the lender of the due on transfer clause.