I have found two broken-solder pads from bottom RAM slot that makes random crashes and restarts. I have these problem many time and I run with only with top slot.
It was very hard to make a good solder joint with them but, when I get it, machine is rock solid using both RAM slots.
Check it touching different slot zones getting some pressure and see if machine crashes to see if it is a problem with RAM solts.
Good luck guys.