27" iMac keeps restarting after RAM upgrade

I have tried two different types and size of RAM and both times after install my iMac just keeps restarting. When I put the old memory back in it works fine again. The computer came with 4 sticks of 2GB Samsung memory. On the first try I put in 4 sticks of 4GB PNY memory. Second try was from PowerMax and they said I could go up to 32 so I put in 4 sticks of 8GB Crucial memory.

I have safe booted and reset the PRAM with no luck. The computer takes me to login, lets me login and then restarts.

Any help would be greatly appreciated.

2010 27" iMac running Yosemite

Thank you