iPhone is jailbraked and unlocked. I bought it two months ago and it had 1.1.2 on it, next day I upgraded it to 2.0 and then I was able to go to 2.2.1. After that all seemed to be OK, but after week or bit less my phone shut down for a first time. At first, I thought that its bricked, but after doing some research I found possibility to reset using home+hold, but problem itself still exists. Usually I find my phone in that condition in the morning and its very annoying. Sometimes it also shuts down durning day, but I have never had this situation at the time I am using my phone(but ~3 times it also has restarted itselt at the time I am using it) What to do?