Amtrak trains run on freight rail, especially out West. The Northeast Corridor is the exception, because Amtrak owns that track. What that means is that the tracks are not made for passenger travel, they are made for freight trains and as a general rule, the freight does not mind that the cars sway and bump as they ride along. We passengers do.
A couple of things to help you deal with the swaying of the cars. If you are worried, purchase a seat in the lower level of the passenger cars, if possible. The car is closer to the rails and so the sway is much less than the upper level. When you walk through cars (besides masking), make sure you always have one of your hands on the seats in coach, or a dining room chair in the dining room. If the car moves unexpectedly, you have something to hold on to.
When in your bed, try to lean close to the walls of the car, rather then the end of the bed, so you do not get pushed out, if you get a bump from changing tracks, or anything like that. If on the upper bunk, definitely connect the straps that are there for your safety. They will keep you from falling out of your bunk in the middle of the night. I personally have no problem with the car swaying and neither does my husband. I sleep well and only seem to wake up, when we reach a station stop. Of course, the interest in seeing where we are, tends to wake me up. The fact that I may actually have cell service for a few moments is also a valid reason for checking things out.
I am sure some passengers may be sensitive to motion. If that is the case, you may want to take along Dramamine, or other motion sickness pills. They tend to make you drowsy, which might not be a bad thing on a train trip, especially at night.
No matter what, knowing what to expect and bringing things to help you if you need it, is key to having an uneventful journey.
