There are advantages to shop jobs like Engineer Spike listed. I started out in the shops as a laborer, never dreaming I'd end up a clerk/agent. But I got cut off, so I went on Line of Road. Mostly Extra Board. I, too, did not like the rotating shifts, never knowing when I'd have to work, when I'd be working. Weekends were scarce. And many of my off days were in the middle of the week. After a few years of this, jobs once became available at the shops. I also got wind that many clerk's jobs would be going away due to automation and consolidation. I liked the Agency work better than shop work, but I did not like the hours, and it would be many years before I stood for 1st trick. So I bid back to the Roadway Equipment Shop in the Material Management Dept. This was 7AM to 3:30, Mon thru Fri and that was just too good to resist! People somehow think that trains are all there to railroads; Everybody just must be an engineer!
But there are a lot of good jobs on railroads, and diesel mechanic is one of them. This can turn into a traveling mechanic IF its something one wants, and other positions, too. The mechanics (we called 'em "pump knockers") follow the traveling gangs and repair track machinery. So you have a lot of options to choose from.