Wrinkled paper

Many possibilities can cause this....

The Pick Up Rollers could be worn out and not picking the paper up correctly.

Something blocking, or catching in the paper path

The Fuser unit rollers could be sticking, going bad..

The Exit Delivery could be warped, cracked.
After these machines get old, the heat from Fuser unit causes the delivery Exit to melt, warp, and become extremely brittle.

The simple things you can check your self:
Entirely remove the paper tray, look in the copier where the paper tray slides in, look in side the machine where the paper tray goes, make certain there is nothing in the trays path.

Take the paper out of the paper tray, go through the paper make certain there is no crumbled paper in the tray, it should lay flat and even in the tray...

My favorite, check the paper it self.

I once was at a customer whom recently changed their paper supplier; every 10th piece of paper was creased from the new **** of paper. I found that the entire Box of paper had creases in every ****. It was the paper not the machine. It was pre-wrinkled.