Yosemite Grey Screen with 3d Party SSD not a trim issue
try resetting your PRAM and SMC, this may resolve your issue, 

http://osxdaily.com/2010/11/15/reset-pram-mac/

http://osxdaily.com/2010/03/24/when-and-how-to-reset-your-mac-system-management-controller-smc/

otherwise it could be bad RAM... take your Macbook in to apple and have them test the RAM.