From my limited experience with DVD players, this problem is most typically a problem with the spindle drive motor - which spins the DVD and allows the laser light beam to read the information off the disc. The problem is hardly ever the laser or the laser lens. Unfortunately, those spindle motors do not have any serviceable access, so actually repairing the faulty motor itself isn't an option. Conceivably the spindle motor assembly could be replaced with some amount of trouble (it's probably held in by four screws and a couple of ribbon cables that attach to a power control board), although I'm not sure where you would obtain a replacement motor, except from an equivalent model that was being sold for parts.
We had a Phillips DVD player that had something of a similar problem, where we could tell that the spindle was not spinning when the DVD was loaded. We did find that if you physically spun the DVD (clockwise), the spindle motor would actually "kick-in" and spin on its own, and the DVD would load and play just like normal. This was only a little inconvenient, and we did have to cut a small access hole in the tray slide cover to "spin" the disk - but it did work, and saved us from having to buy another DVD player. Good luck.