iPhone 4, blue screen and restart

Hey guys since i got my iphone (2 weeks) sometimes the screen will randomly go blue and restart. i restored and took it to the apple store, they said nothing was wrong but if it happened again to bring it back.

the first time i JB with green pois0n, the second time with limera1n and i still get this random blue screen at random times and the phone just retarts. after it happened again yesterday i restored again (and did not JB) but i havent been able to trigger the blue screen again.

is this happening because of a JB app issue or is it a hardware problem?

Thanks

the screen literally just goes blue then restarts. i dont know if its because of lack of memory because ive had it happened within 5 minutes of each other, its really getting annoying.

since i restored it has not happened again but i am not JB right now.

JB apps installed:

activator
bite sms
sbsettings
winterboard
safari tab closer
remove background
springflash
springflash sbsettings

Themes:
glasklat HD ipad and iphone 4
serious sbsettings hd
bitsms no pink retina

went to the apple store today, could not replicate the problem but on good faith he just replaced the phone for me