I received my new Razr M last Wednesday and after getting the phone 50% charged, it started to get a little warm and started to reset itself on its own. It continued to reset after partially loading until the battery completely drained itself. I let it sit overnight, plugged it back in and it took a full charge and ran well for about a half a day before it started to do the same thing. This time it got warm again so I placed the phone in the refrigerator for five minutes to cool it down and that amazingly fixed the problem for a little while. Now, every time I use the phone for about ten minutes, it does the exact same thing and the only remedy I've found to fix it is to put it in the fridge to cool it down so it starts working again. I've tried starting in safe mode and I've done a factory reset and neither fixes the problem. The phone doesn't get all that warm before this happens so I'm at a loss as to what it could be.
This is certainly not normal behavior. Is the Razr M a new phone or a CLNR? If new you have 14 days to get a brand new replacement. Are you in an area with no service causing the phone to continually search? Do you have many, many files trying to sync; photos, music, social media, etc? Try turning off sync and see what happens. Try operating in Safe mode for a day and see if it's an app that you loaded that is causing the problem. Finally, try a factory reset. If all fail to solve the issue, then get a replacement, because something is definitly wrong with hardware or firmware.