A true 4-minute Tabata set is pretty much to metabolic failure. You should be absolutely done at the end of it, and need at least a 3 minute rest before doing a new set.
A guideline I like to use is that if I feel rested enough to do another set at anything less than 3 minutes, I didn’t push it hard enough. I usually use a 4 minute rest interval after a set, with 4 sets per workout.
Also, to really benefit from doing Tabatas, doing them multiple days per week for a matter of weeks is the way to go about it.
Try doing them about 4 intervals per day, 5 days per week for about a month and see where you get.
