I don't feel that the M-05 is particularly stable in a straight line with stock steering. M-05 Pro parts are a little better, even more Tamiya blue hop-ups are probably better still!

Because it is happening one or two laps in to a run I wonder whether it has something to do with the balance of the car changing a bit once the tyres come up to temperature, and exposing the straight line problems.

Tell us a little about your setup and track and we might be able to identify the problem.