Iphone 4 "no service" after using apps?

I just want to ask if anybody here who experienced this... after using an app like playing games on iphone 4, the signal goes down and finally to "no service". I did a hard reboot and then the Iphone goes to recovery mode ( Stuck) and telling me to restore... . "BUT" when I turn off the iphone and plug it to the USB to the computer to restore,,,everything goes to normal ,I got signal and everything even if I did'nt restore it yet. this is weird and annoying.is there any fix for this? thanks everyone