Phone reboots intermittently

[mdasent]

Hi I recently started getting this problem (3 days ago). My phone would stop responding where i couldnt use the touchscreen only the keyboard or vice versa after awhile it would reboot for itself and work fine. this happens about 4 times a day very frustrating. Ive already upgraded to the newest OS using a full device wipe with BBSAK and manually reinstalling the apps. Ive had this phone over a year now and never had a problem. I wondering if i should warranty it before the warranty expires or if their is a fix for this (im still trying to decide wich OS 7 device to get 9900 Full touch Torch or 9810)

anyone have ideas

Marlon