Willie
I've had no problem sleeping aboard railroad sleepers. I've ridden them everywhere from USA to Mexico to Chile to Australia and slept very well. I think that after spending most of the day on the train, one gets used to the rocking motion by the time bedtime comes around. In any event, the rocking is generally not so bad.
Consider the alternative...
I've done that many times as well. A flat bed is far preferable to a coach seat. One thing that works for sleeping in coach seats is complete consumption of at least a pint bottle of your preferred distilled alcoholic beverage.
If you've never traveled on an overnight train in a sleeper, do yourself a favor and try it out!
[This message has been edited by Seat 2A (edited 12-24-2001).]