Strange text messages at five minute intervals with no sender So I've been having this problem recently where I get these extremely strange text messages being sent to my phone. They have no sender associated with them, and just look like a bunch of gibberish. Here is a screenshot:

http://i.imgur.com/bl2Al.png

Currently, I am getting the same message multiple times every 5 minutes. At first I just sort of ignored it, and one day I decided I would just go ahead and delete all the messages. As soon as I deleted them, they just kept on coming back at 5 minute intervals. 

I am on Sprint on the Nexus S 4G

My phone has also been doing other weird things lately. Sometimes when I lay it flat on a surface, it will just reboot itself constantly. I'm not sure if this is related to the text messages or not. 

Also, the messages only show up in the "Messaging" app which I don't really use. They don't show up in Google Voice at all. 

EDIT:

I actually got some of these weird messages about a month ago, however they stopped for a good while. Today, I just decided to delete them, and now they've been coming in every 5 minutes. So far I've received 32 in the span of about an hour. I have not talked to Sprint about this, and I don't believe I have been charged for them. Also, I can't reply back to these messages. If I try to reply and I hit "send", it just tells me that the message was not sent. 

EDIT 2: 

Factory reset the phone. The messages are still coming in.
Questions for you:


Did you install an app recently? 
What app did you last install? 
How long was that going on for? 
Have you checked with your Sprint provider? You're not getting charged for those incoming messages? 


It sounds like mal-ware, but do not wish to raise alarm nor fear in you, BUT by answering my questions above to ascertain it.

Quite possibly, it sounds like a scam, if you were to reply innocently like "Who are you?" you could be charged premium rates for sending it. 

As for the gibberish, its likely in a language that is not recognized by your handset hence the font shows the "gibberish" character as a result.

IF all else fails, try a factory reset the handset at last resort.

Edit: Based on your edit, it sounds like its stopped for a good while due to perhaps its hit the threshold limit of how many SMS to be stored, then when you went to delete them, more kept coming in. 

The apps do seem legit.. btw :)

Would you not suggest try this, download this app called 'History Eraser' from Google Play, to wipe out the history of the SMS, just that specifically alone, and nothing else. See if that helps. If more are still coming in, then I hate saying this, factory reset the handset to clear out whatever it is that's causing the jam.