Some possible causes that come to mind:
Tonearm wire dressing
Check that the wire leading from the arm is not kinked or catching on anything.
Antiskate mechanism malfunctioning
Try moving the A/S adjustment back and forth through its full range a bunch of times. Also, try setting it to "zero" and test the arm's behavior for a few days. I don't know how that mechanism works, but I suppose something in it might be "sticking".
Bearings dirty, worn, damaged or out of adjustment
Repairing this would probably be a job for a pro. Try holding a stethoscope against the bearings and move the arm through stickiness until it frees up. You might be able to hear where the problem is.
Duh #1
Make sure the end stub isn't snagging on a dust cover or any other object (the cat?) that might be in the way.
Duh #2
Make sure the arm's cueing support bar and the underside of the arm tube are clean. You can use a little alchohol on a Q-tip.
If the cause is something like the last two you're allowed to make something up rather than confess in public! ;-)
Others will have other ideas I'm sure. Good luck!
Tonearm wire dressing
Check that the wire leading from the arm is not kinked or catching on anything.
Antiskate mechanism malfunctioning
Try moving the A/S adjustment back and forth through its full range a bunch of times. Also, try setting it to "zero" and test the arm's behavior for a few days. I don't know how that mechanism works, but I suppose something in it might be "sticking".
Bearings dirty, worn, damaged or out of adjustment
Repairing this would probably be a job for a pro. Try holding a stethoscope against the bearings and move the arm through stickiness until it frees up. You might be able to hear where the problem is.
Duh #1
Make sure the end stub isn't snagging on a dust cover or any other object (the cat?) that might be in the way.
Duh #2
Make sure the arm's cueing support bar and the underside of the arm tube are clean. You can use a little alchohol on a Q-tip.
If the cause is something like the last two you're allowed to make something up rather than confess in public! ;-)
Others will have other ideas I'm sure. Good luck!