My macbook pro troubleshoot reset with grey screen My macbook pro is MacBook Pro (13-inch, Mid 2012), 8G ram, and run OS 10.10.4.
I have upgraded storage from 500GB HDD to Crucial M550 SSD. I removed dvd drive and use optical bay to keep 500GB HDD as the second storage.
I have reinstalled my OSX after upgraded

After upgraded, my macbook pro temperature alway hot (>70 C degree) when I open a lot of applications and a lot of chrome tab.

Sometime My macbook pro auto reset with grey screen 

 

Please help me. I can work with this situation. 
Thank you.
The first rule of computer troubleshooting: "isolate and identify."

Which basically means undo any changes you made recently. If you plugged a new mouse in, remove it. If you installed a new app, remove it, etc.

In your case I would remove the drive in the optical bay and put the Apple optical drive back in and see if the issue repeats.

User "n1000" hints that it might be related to an OS upgrade or your specific model of Mac. If you can go back to the previous version of the OS that would be good (though time consuming).

You could also take the Mac to an Apple store and have a Genius run some diagnostics and see if it is a warranty or known issue. Note, Apple will blame the SSD in the optical bay so you will have to put the optical drive back in for Apple to diagnose the issue beyond blaming the SSD and sending you on your way.