How can I stop Samsung Galaxy Spica restarting itself in a loop?

I recently bought a used galaxy spica its in really good condition and etc..but when i launched it up there is something fishy going on... It restarts in a loop... As in, it boots up, i can use the phone for around minute or so, then it restarts...then again i can use it for a minute or so...and it restarts...i cant call or anything cause it restarts all the time. It has been updates from the original 1.5 to 2.1 eclare, if you know a fix, please do tell.