If this is not normal ie you have had no delay in the past and now you are it may well be an Excel virus and it is already in your computer memory launching a new file may take a few seconds when the macro is trying to infect this new file and replicate itself.
This was something I found when the first Laroux virus came along.
In Excel call up Windows Unhide, see if you have got a mysterious new file thats hidden In many cases you will find one there called Personal (This is often the case).
If there is nothing there then this is a good sign,
Also go to VBE Alt F11,
Check to see if in the list of active modules you also have an extra file that you did not realise.
Hope this does not scare you too much but It is worth while checking, In a previous role I was sent one of these files about 8 years ago from our US headoffice. I was consolidating all European countries about 30 locations sending out files that were used by them. Thanks to this I had 2 spend approx 3 days appologising to everyone and sending out a fix on the macro to get the virus deleted from all the files on the network.