A warm plug (either end) may indicate some physical fault with the power cord: too much resistance or load, heats up....
Still your existing power cord may have some physical problem that interfers with making a solid electrical connection to the PSU prongs. And that end tends to be a bit tougher to physically plug in to begin with.
Then, if you are plugging it in while electrically live (i.e., plugged into the outlet) some arcing/sparking is taking place before the two ends are fully mated.
Plug in the PSU end first, make sure the plug is fully in place. Plug in the outlet end and see if the snappy sound stops.
If not, try another power cord and again plug in the PSU end first.