Switch off the machine and unplug from the mains. Pull out the paper tray completely and inspect both the paper (for tears, wrinkles etc) and the paper location guides. Ensure that the guides maintain the paper in the correct position within the tray. Check the paper pick up roller (if you can find it). There will be one, normally found at the front or rear of the machine, sitting just above the top/bottom edge of the paper. The roller may be worn or dirty. A temporary fix can sometimes be achieved by cleaning these rollers and the associated separation pad (a strip of rubber which prevents multiple sheet feeding) with a dry cloth dampened at one corner with soapy water. Then dry the roller thoroughly.

If it is not the paper tray at fault then try removing the toner cartridges or fuser and look for anything that may be obstructing the path of the paper in this area. Sometimes, a sticky label is the culprit because the previous user of the printer is now one or more sticky address labels missing. You could also try a new toner cartridge or new fuser unit if you have access to one. If after trying these methods the problem persists, then sorry but you need an engineer.

Good Luck.