Smartphone Re-starts Continuously.
Some Smartphones may re-start continuously and it will not allow you to make or receive calls or to do any other tasks. First thing to do, replace the device with another SIM card. If it solves the problem, go to your carrier agent and get a replacement SIM card by providing your old SIM.
Changing of of SIM card didn't work for you?
In this case, the device may require a factory reset. If you can do that by yourself 99% the problem will be solved. There are many factors behind this continuous re-start problem in hand held devices.
To do factory reset, follow the instructions given by your Smartphone manufacturer.
If you are going to request your phone repair center to do the job, ask them to backup all your data from the device.
Then remove your SIM card and memory card from the device.
After this you can provide the phone to the repair shop.
Once the factory reset job is done, you can have your phone in proper working condition when you place your SIM card and the memory card. You will have to feed your username and passwords for your mail account and other social media net work connections to function in your smart device.
This process can be done by yourself, if you follow the steps according to the manufacturer's instructions.
You can complete the task within 30 minutes of time.
If you give it to the repair shop they may take one day, to perform this service.
Samsung Smartphone Factory Reset. samsung.com FAQ