At first glance, this looks like a simple problem:

Computer won’t start. I re-seat the RAM, and it starts correctly.

I close the computer case, and when I start the PC again, I hear a familiar beeping sound (no RAM).

Since there isn’t much dust inside the PC, I re-seat the ram again, and I can eventually get the PC to start long enough to run a RAM test… but I find no fault… and  the PC is now working fine, and I can’t re-generate the fault.

I ask the customer to keep an eye on it, and to call me if it happens again.

Well, I get called again just 1 month later… with exactly the same problem.

So all I can figure is that the RAM has an intermittent fault, so I replace the RAM.

Oddly enough, that seemed to fix the problem.