Is your Lexmark MS310 printer displaying the "load paper" error with a full paper tray?
If so, there may be an issue with the pick rollers in your paper tray. When a print job is sent to your printer, a set of rollers known as paper feed rollers make contact with paper in your tray and pull the paper into the machine. If the "load paper" error pops up during printing and your paper tray is full, it's very possible that your paper feed rollers are worn or dirty.
Paper feed rollers can wear down over time or accumulate dust and paper fibers. If either occurs, the rollers can lose their grip making it difficult or impossible to pull in the paper.
A temporary fix for this problem is to clean the rollers using a Q-tip dipped in distilled water. This can temporarily remove any debris perhaps allowing you to print for a time. The permanent solution is to purchase and install new rollers for uninterrupted printing.