Starting again yesterday (this happened in January or February, too), my Note 4 constantly starts and restarts over and over. It shuts down suddenly in the middle of tasks. I've cleared the cache, have only 1 app running at a time, have a full battery, etc.
Last time, there seemed to have been a software update that caused this. Has there been an update recently? I can't even get the phone to stay on long enough for me to check.