more info on your phone/issue please... is it just stock (not rooted, no mods, etc), do you have a lot of apps on it, has this problem been happening since you got the phone or recently, does it happen all of the time, only at certain locations etc.
I would install cwm and wipe the dalvik and cache, then reboot to try and fix this...
also, update you prl
you can find info on clockworkmod (cwm) under the all things root thread, that will give you the ability to wipe the dalvik and cache
is the phone fully activated with boost?
you could take the phone to a boost shop to see what they think, or if you are a DIY type you could try the update tool by zte to reload your phone and start from there