engine storage

[hamlitonohio]

I have a train set that I put up every Christmas, the issue I'm having, is the engine moves very slowly and sometimes it won't roll at all, what can I do, I store the engine and the rolling stock in a box in the basement

[jbrock27]

What scale?
Have you ever taken the shell of the locomotive off and cleaned and lubricated it where appropriate?
Have you ever cleaned the wheels of the loco?
Have you ever cleaned the track?