Okay, so I guess that when you say the first few shots are not as CONSISTENT, we're not referring to velocity as such, but that the impact points aren't where you would like / expect? Are these first few shots generally striking lower than the subsequent shots? Is this pattern the same at all ambient temperatures, or does it seem more prominent in cooler conditions?
Our synthetic piston seals expand and contract at greater rates than the steel cylinder. So, in very cold temperatures, the piston seal will be a looser fit in the cylinder. The reduced friction could result in quicker piston acceleration. The temperature produced by the springer firing cycle will warm the seal up and cause it to expand ever so slightly after a few shots. If left in the cold unused for a good few minutes, it may need "warming up" again. If a piston seal "standard fit" is a little too tight, when used in higher ambient temperatures it might become even more evenly tight, creating excess friction and robbing power. And I know of at least one user on here who, when using the rifle in extreme cold, experienced such drastic loss of piston seal contact that the rifle would not fire a pellet! Once the rifle was "re-acclimatised" it was fine, and the piston seal fit must have been on the very loose side.
Hope this might help a little with your concerns. Most serious shooters (if hunting or shooting a comp) will have a few test shots to firstly check all is good and this also has the added bonus of "stimulating" the action.