Don't play with the adjustment pots until you clean the optics. I used 99% isopropyl and a lint-free swab. The lens itself is probably relatively clean, but is easiest to get to. If you take the cover off, you'll basically be staring right at it. Clean it, and if the problem persists, carefully remove the plastic assembly containing the lens, and clean off the prism underneath (you'll see it; it bends the laser beam 90° up through the lens you just removed). The surfaces which face upwards are most likely to need cleaning, but clean them all while you're in there (including the one which faces the laser).

This cured mine of the exact same problem. IIRC mine didn't spin either; the laser assembly does a focus cycle to figure out if there's a disc first. If the optics are dirty it can't focus on the disc, assumes it's a transport error, and ejects the disc.