UPDATE
Ran Task Manager to see what was hogging resources as I opened a Cubase project that had been overloading the Audio Processing Meter and sure enough found the culprit to be the RAM which was going over 80%. I was glad but also puzzled to find this because last year I upgraded the RAM from 4 GB to 8 and at 4 GB I had no problems! I ran a test to check the RAM but found nothing wrong.
Anyway in the end I bought a new laptop with 16 GB RAM and problem is solved for now…