When I had a choke cable that wanted to go closed as the tractor ran, this is what I found.
At some point in its life, the choke spiral outer sheath, and inner wire had been "kinked" when the choke was out.
When you pushed the choke "in", the bent wire was pushed away from the matching spot of the kinked outer sheath.
The vibration of the engine was enough to make the inner wire, and outer sheath move so that they would match again.
I happened to see the sheath move as I pushed the choke button in and out.
I bent both the sheath and inner wire back to a kinda straight condition, that stopped the "self moving choke button"...
If you can not find the problem spot, simply replace the cable assembly,
that will fix it.
