Iphone 3Gs or 3G problem and Ipod touch problem?

[Lowz]

I got an Iphone 3G or 3Gs from my uncle (the one with white cover on the back).. and when i use it suddenly turns off and won't turn back on regardless any button i press... Sometimes it turns back on when i connect it to my computer.. and then it repeats so how can i fix this??? I found Cydia on the Iphone so that voided the warranty.. So downloading something Cydia caused this or is it just the battery that might not work?? Also, i have any ipod touch 1st Gen that won't turn on.. and when i connect it to the computer it makes me restore it... and evenually during the restore error 1604 or 1603 pops up... Jailbreaking issues?? Any help