There are certain instances of this occurring but we do have physiological systems.
Generally? If you look at these stories there are two that are commonly stated. Drowning in Cold Water. And Hospital Near Death.
Okay Firstly lets look at Drowning…
Drowning in Cold Water can keep you alive. Your entire body requires a certain temperature to work. You need to stop thinking of yourself as biology and start thinking as chemistry. In these situations if you are removed from water you may appear dead. Your body temperature would be much lower and your pulse and heart rate would be all but absent. If you are warmed up correctly? You may have had enough oxygen to keep surviving while your overall O2 demand would have been low enough to prevent cell death of vital organs. Its rare but it has happened. The issue is you aren’t dead but appear so.
The second one is hospital near death. This one’s a failing created by TV. And for this we need to look at how a defibrillator works. It doesn’t restart stopped hearts. It STOPS hearts. When you have fibrillation or random uncoordinated contraction of the heart, blood does not pump. A defibrillator electrocutes your chest and your heart stopping it. It is hoped that your pacemaker would then take over and beat normally. This looks like angry squiggly lines on the heart monitor. Not the flat line.
A flat line means the heart has stopped working completely. So when people get CPR and Defib they assume they were clinically dead because TV shows show the event faultily.
A lot of these events occur in places where medical coverage is not so great. Stethoscopes are sensitive but are subjective and you can miss sounds that are important. A quick googling shows a lot of these miracles occur in places far away from the medical systems we take for granted. Rural India, China, Zimbabwe, Zambia, Brazil. A handful occur in small towns in the USA but there are technological issues like hypothermia induction involved. Frankly? These have never really been miracles. Just interesting events that sometimes can occur.
Not divine miracles.