Please:
1. Run the 'Extensions' app and check you don't have any non-Ubuntu extensions enabled. If you do then please turn them off.
2. Immediately after the next freeze please run:
journalctl -b0 > journal.txt
and then attach the resulting file here.
3. Also leave 'top' running in a Terminal window and tell us if any process is using high CPU, particularly around the time of a freeze.
Please:
1. Run the 'Extensions' app and check you don't have any non-Ubuntu extensions enabled. If you do then please turn them off.
2. Immediately after the next freeze please run:
journalctl -b0 > journal.txt
and then attach the resulting file here.
3. Also leave 'top' running in a Terminal window and tell us if any process is using high CPU, particularly around the time of a freeze.