You may have a roller that is dirty. Get a can of compressed air and spray it into the paper return (where it comes out at) being sure to hit the rollers really good.
It could also be that the fuser is trying to quit seeing as to how you said that papers will coil around the back part of the printer (this is usually caused by the toner not melting completely to the paper after it passes through the fuser assembly)
Also, have you ever replaced the drum on this unit? I'm assuming this is a laser printer.
If you haven't, it may be time for a replacement drum.
Also most printers have a built in cleaning cycle, you can try running that and see if it helps.
The user's guide for it can be found
HERE . Take a look at the troubleshooting section and see if any of the situations fit as to what is going on.