You basically need to stop the states on the borders of Rome from being influenced by Rome, which is obviously pretty much impossible.
The Third Century Crisis happened largely because Rome's neighbours (principally the Iranians, but others too) had begun to acquire, through generations of interaction with Rome, the necessary tools for dealing with the Empire. In the case of Iran it was the emergence of a powerful centralised monarchy in the house of Sasan, elsewhere it was economic development brought on by the trade and foreign aid policies of the Empire.
Developments that had been ongoing since Augustus' day are always chronologically likely to come to a head in the third century, in my view. Now, you can have Rome deal with them better by having a strong dynasty in place between 200 and 300, and butterflying the various contemporary plagues, but after 200 Rome in any TL is always going to face a difficult period, in my view.
The whole political/strategic basis of the Principate rested on overwhelming military superiority on all frontiers, and it's not going to be possible to keep this up indefinitely.