Hi Ryan!
It does sound like CPU/GPU issues here. You can try to reflow them and see how it goes!
Here is a guide regarding the reflow: [guide|3654] (this is meant for the PS3 Phat, but just to give you an idea). Always make sure to use new thermalpaste afterwards!
A reflow is most of the time temporary, but then you can see if it was related to the CPU/GPU.
Please let us know how it goes!