Lightroom slow to launch

The latest incarnation of Lightroom (CC) is very slow to launch (can take over 10 minutes before any images load). I've had a couple of chats with Adobe and the issue has been resolved although not for very long. 

I have an iMac purchased in April with 

• 16 GB 2133 MHz DDR4
• 2.3 GHz Dual-Core Intel Core i5

Although it's included in my subscription, I cannnot use LR Classic without running out of application memory in a few minutes.