If you stop training, you should be able to continue from where you left off. I called 'train' on the basic grid world example a couple of times in a row and the output of 'getLearnableParameters(getCritic(qAgent))' was different. You can always save the trained agent and reload it as well to make sure you don't accidentally delete it.
Update:
There is a regularization term added to the loss which causes the other entries to change slightly. To avoid this, you can type:
qRepresentation.Options.L2RegularizationFactor=0;
