Ubuntu 20.04 running slow with low CPU usage

Just got a brand new install of Ubuntu 20.04 and it's running rather slow.
I was using 20.04 before and it was snappy, recently I had to get rid of that and start again.

I've got largely the same programs with the only notable exception being that I'm using Brave instead of Chrome.

• CPU : Intel® Core™ i5-4460 CPU @ 3.20GHz × 4
• GPU : GeForce GTX 960
• RAM : 16 gb
• Motherboard : ASUS H97-PLUS

My system is on an SSD, there is an old HDD in the PC but it's not even mounted. I'm using Nvidia's driver nvidia-driver-440.

Clicking on windows is regularly taking a second to respond. Things like the windows key take 3ish seconds to show up.

When looking at the CPU monitor I'm very low on usage. Currently they are all hovering around 10 - 20 % (I have 2 docker sites running and 2 IDEs atm, but it's slow even with them off).

The only difference from my previous install is Brave. Any thoughts as to what's up?

Output requested in comments :

top - 12:10:24 up 1 day, 11:06,  1 user,  load average: 1.54, 1.18, 1.03
Tasks: 323 total,   1 running, 322 sleeping,   0 stopped,   0 zombie
%Cpu(s):  6.0 us,  6.0 sy,  0.0 ni, 86.6 id,  0.0 wa,  0.0 hi,  1.5 si,  0.0 st
MiB Mem :  15957.1 total,    385.9 free,   5461.7 used,  10109.4 buff/cache
MiB Swap:   2048.0 total,   2027.5 free,     20.5 used.   9805.5 avail Mem 

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND  
 425028 root      20   0       0      0      0 I  13.3   0.0   0:34.39 kworker+ 
 425952 derek     20   0   12328   4272   3440 R  13.3   0.0   0:00.02 top      
  81097 derek     20   0 4600000 307664  60224 S   6.7   1.9 126:07.64 gnome-s+ 
 373735 derek     20   0  701512 266396 194588 S   6.7   1.6  24:22.77 brave    
 407238 derek     20   0 5150596 576008 181840 S   6.7   3.5   7:48.28 brave    
 407758 derek     20   0 7389168   1.1g 129720 S   6.7   7.4   8:55.13 java     
      1 root      20   0  171424  13468   8252 S   0.0   0.1   2:16.71 systemd  
      2 root      20   0       0      0      0 S   0.0   0.0   0:00.03 kthreadd 
      3 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 rcu_gp   
      4 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 rcu_par+ 
      6 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 kworker+ 
      9 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 mm_perc+ 
     10 root      20   0       0      0      0 S   0.0   0.0   0:04.39 ksoftir+ 
     11 root      20   0       0      0      0 I   0.0   0.0   0:57.04 rcu_sch+ 
     12 root      rt   0       0      0      0 S   0.0   0.0   0:00.33 migrati+ 
     13 root     -51   0       0      0      0 S   0.0   0.0   0:00.00 idle_in+ 
     14 root      20   0       0      0      0 S   0.0   0.0   0:00.00 cpuhp/0  

derek@DPCU:~$ free -h
              total        used        free      shared  buff/cache   available
Mem:           15Gi       5.3Gi       395Mi       399Mi       9.9Gi       9.6Gi
Swap:         2.0Gi        20Mi       2.0Gi

derek@DPCU:~$ sysctl vm.swappiness
vm.swappiness = 60

derek@DPCU:~$ la -al ~/.local/share/gnome-shell/extensions
ls: cannot access '/home/derek/.local/share/gnome-shell/extensions': No such file or directory

derek@DPCU:~$ la -al /usr/share/gnome-shell/extensions
total 20
drwxr-xr-x 5 root root 4096 Apr 16  2019 .
drwxr-xr-x 7 root root 4096 Jun  1 00:54 ..
drwxr-xr-x 2 root root 4096 Jun  1 00:52 desktop-icons@csoriano
drwxr-xr-x 3 root root 4096 Jun  1 00:52 [email protected]
drwxr-xr-x 3 root root 4096 Jun  1 00:52 [email protected]

derek@DPCU:~$ sudo dmidecode -s bios-version
[sudo] password for derek: 
2504

derek@DPCU:~$ sudo lshw -C memory
  *-firmware                
       description: BIOS
       vendor: American Megatrends Inc.
       physical id: 0
       version: 2504
       date: 05/20/2015
       size: 64KiB
       capacity: 8MiB
       capabilities: pci apm upgrade shadowing cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer acpi usb biosbootspecification uefi
  *-memory
       description: System Memory
       physical id: 44
       slot: System board or motherboard
       size: 16GiB
     *-bank:0
          description: DIMM DDR3 Synchronous 1600 MHz (0.6 ns)
          product: KHX1866C10D3/8G
          vendor: Kingston
          physical id: 0
          serial: 762EEA49
          slot: DIMM_A1
          size: 8GiB
          width: 64 bits
          clock: 1600MHz (0.6ns)
     *-bank:1
          description: DIMM [empty]
          product: [Empty]
          vendor: [Empty]
          physical id: 1
          serial: [Empty]
          slot: DIMM_A2
     *-bank:2
          description: DIMM DDR3 Synchronous 1600 MHz (0.6 ns)
          product: KHX1866C10D3/8G
          vendor: Kingston
          physical id: 2
          serial: 682EDE32
          slot: DIMM_B1
          size: 8GiB
          width: 64 bits
          clock: 1600MHz (0.6ns)
     *-bank:3
          description: DIMM [empty]
          product: [Empty]
          vendor: [Empty]
          physical id: 3
          serial: [Empty]
          slot: DIMM_B2
  *-cache:0
       description: L1 cache
       physical id: 52
       slot: CPU Internal L1
       size: 256KiB
       capacity: 256KiB
       capabilities: synchronous internal write-back
       configuration: level=1
  *-cache:1
       description: L2 cache
       physical id: 53
       slot: CPU Internal L2
       size: 1MiB
       capacity: 1MiB
       capabilities: synchronous internal write-back unified
       configuration: level=2
  *-cache:2
       description: L3 cache
       physical id: 54
       slot: CPU Internal L3
       size: 6MiB
       capacity: 6MiB
       capabilities: synchronous internal write-back unified
       configuration: level=3

AMI H97-PLUS

You have BIOS version 2504 from 05/20/2015.

A newer version, 2603, from 03/25/2016, can be downloaded here or here.

Note: Have good backups before updating your BIOS.