Preferred Roaming List probably won't help you in this situation. Updating the profile could if something has become corrupted. Also, if you're rooted, you could try clearing all your caches and see if that improves your situation.
Your picture just shows that you have a weak signal. Not "nothing at all". There's usually a "X" if you don't have service. Settings-> About Phone-> Network/Status. Under Signal Strength you'll see you signal in dBm. If you don't have a signal it'll say so too.
Signal strength is a reflection of congestion and other factors on the network, or a tower. You can download something like Open Signal Maps to see which tower your phone connects too. Then move around till you can get your phone to connect to a different tower. If the problem is solved then you know it's a tower issue for whatever reason and not your phone. Restarting your phone also causes the phone to locate a new tower.
