If you look in this screenshot, you can see that the swap is completely full even though you have plenty of ram left over. either disable swap or reduce swappiness to 10.
use
cat /proc/sys/vm/swappiness to check present swappiness and sudo sysctl vm.swappiness=20 to reduce it to 20.
A swappiness of 60 means that your system starts swapping when your ram is 40% full.
A swappiness of 20 means that your system starts swapping when your ram is 80% full.