Yes, my laptop once had RAM which cause it not to start up but I fixed it by cleaning the gold edge contact at the end of the RAM and re-installing the RAM.
Yes I did, it was with the computer I had a few years ago, and what happened was that I would get a bunch of parity errors and BSODs and then it would shut itself off unexpectedly. I had 3 128mb sticks of RAM, and I had to troubleshoot because I wasn't sure if it was the memory slot that was bad, or the stick itself. Thankfully, it was the stick, and on the very first try, I found the bad one. So I replaced the bad stick with a different one, and my computer has been fine ever since.