You could try taking the housing off and checking to see if there is any dust accumulation on the electronics. (and vacuuming it off, if there is).
If the problem is overheating, a good electronics repair shop may be able to address it without specific experience with scanners. Bad solder joints, or failing generic components could be the cause, and that should be be easily fixable by any electronics shop. I don't know if there is a fan in the unit, but that's another fairly common, and easy to fix failure point (generically speaking).