Commencer à -- to begin to...
Je commence à me sentir en vacances. -- I begin to feel on vacation.
Je commencais à me sentir en vacances. -- I was beginning to feel on vacation.
As you can see, the phrase me sentir en vacances remains the same, no matter the tense. And the English use of "was" is not reflected in the French. In fact, as the above examples demonstrate, you don't need "was" in the English either.