Smart move.
The three buttons are the same as opening the back, removing the battery, replacing the battery, and replacing the back. All user data is retained. This is NOT a "factory reset" that would wipe all user data.
The symptom you describe covers a wide area of possibility. In some cases replacing the device is the solution. In some cases "conditioning" the battery is the solution. In some cases replacing the SIM card is the solution. In some cases making sure the SD card and SIM card are frimly seated is the solution.
They all get lumped together and confused with one another.
Reading other people's experiences I come away with the conclusion that there are bad batteries out there (not all batteries just some), there are bad SIM cards out there (not all SIM cards just some), there are bad devices out there (not all phones just some). A Bionic that is dropped can have its SD card of SIM card come loose.
The key is to get yours diagnosed and corrected while you are still in the exchange period where you can get it replaced if you need to. With luck you can work with the knolegable person where you bought it.
... Thom