Rooted Evo Keeps Cutting Off

[jackets70]

Hey, I'm just a noob at all of this but my evo is fully rooted. Everytime I use the internet(data) or an app that uses a lot of internet, the phone cuts off and restarts. I thought it was the ROM but i just downloaded OMJ's ROM and it did the same thing. I dont know what to do. I am on android 2.2 but i pretty sure I'm old on the OTA. All and any help is appreciated.