How do I make pavers stop shifting when I walk on them?
Sounds like you need a firmer subbase under your sand to spread the load across a wider area.

I would follow the same procedure as for laying a wider area such as a patio. 
It seems like a lot of effort for a small area like the one you have but unless the ground underneath is already very hard and level, the pavers are going to settle unevenly and/or slide horizontally.


Lay a subbase made from a mix of aggregate sizes several inches thick. This type of aggregate locks together nicely and spreads the load across a wider area so no single paver sinks more than the others.
Compact using a plate compacter (tamping down with a large piece of timber or a cinder block would be ok for small areas).
Excavate around the edges and bed the edge pavers in concrete. This prevents the edges of the subbase and sand from crumbling away. Make sure to "haunch" correctly, as shown in this great resource for paving projects.
Lay an inch or so of sharp sand on top and level it off.
Finally, lay the rest of the pavers.