Safari will not load pages on start up
I have a 5K iMac with latest version of OSX and updates and have been experiencing problems with Safari for quite some time (I had two iMacs before this one). When I power up the system, load mail and click on a link which opens up Safari....it just sits there and does nothing. If I close Safari and reload it, it works fine. Also, when I power up, if I load Safari first, the same thing happens and if I reload it it works fine. Start up and shut down times for the software seems very slow. In comparison, Firefox is incredibly quick! I've tried clearing cache and cookies but to no avail and hoped recent updates to the software might sort this out but it hasn't. Whilst reasonably competent, I'm not an expert. Can anyone help? Thanks.