Diagnostics

Electrical

The track plan itself is fairly simple, its basically a loop.  

The type of switches /track may be important.  

Where is the power feeder (hopefully feeders)?

We definitely need more info

It's hard to help without more information. For instance, do you know if your turnouts are power routing? If so only the tracks the points are lined to will be powered. It could be a simple thing like that or it could be more complex. It could be a list of simple things. Help us help you.

Have you cleaned the rails?

Have you cleaned the rails? You may have dirt on them. 

Bench Work Relevance?

I don't know what this means, or what the bench work has to do with anything.

Are you saying you need to give the train/table a little bump (?tapping?) to get it going? That would suggest spotty contact due to dirty wheels and/or track.

Perhaps...

the best first step would be a good cleaning of tracks and wheels, if nothing change there maybe an issue with the locomotive itself.  Might try a test track and see if the engine performs well away from the layout.

Peace, Bill

A few clarifying

A few clarifying questions:
 1- Did you build your layout with sectional (as shown in the plan) or flex track?  
2- Are joints between tracks pieces soldered or not?
3- How many and where did you place electrical feeder wires to the track?

It sounds like you have too few feeders spread too far apart, and that layout benchwork sections are not solidly connected; thereby poor electrical contact from one to the other.  As you step on a spot on the floor and there’s some flex, the sections either push together or pull apart, causing a disconnect in the electrical path of the track.   
As a general rule, you should have a feeder drop on every physical section of the base (About every 3-4 feet, as well as before/after turnouts and on sidings/ spurs as needed).

Easy way to find the

Easy way to find the issues.

Clean your track and your locomotive wheels first and see if that helps. Cleaning the locomotive wheels can be done with a paper tower and some isopropel alcohol, same thing can be used to wipe down the rails.

Next take a tester with the track power on and move along the rails with it till you find a place that lacks power. Look for a poor connection or add a feeder to that section of track. Before long you will have all the track powered.

If the layout worked once it will likely be as simple as those things to get it back into operation.