This can happen if the the paper sensor in the tray is malfunctioning or has dirt over it. You need to remove the paper tray and clean it with compressed air and also clean the printer internally and see result.
If problem persists you will need to get the printer repaired to replace the sensor. If in warranty send it to Canon or else take it to a local repair store. But it will be cheaper to buy a new printer if its out of warranty.
You can try to blow out printer paper area with compressed air, but if the sensor is bad, it might not work.
Please let me know if you need additional help. Thank you.