have an issue with repeated and sudden shutdowns even after running webroot telling me no virus.

Hi rgormley
 
Welcome to the Community Forums.
 
I am no Mac expert but usually random shutdowns are caused by some issue with hardware or drivers.  Have you recently made any such changes to your system? 
 
Looking around on the Internet and searching based on 'random Mac shutdowns' or a similar search string reveals a plethora of support forum articles on the subject some of which are relatively recent.  I would therefore try that and see what specific information is on offer.
 
If doing so please do bear in mind that whilst there are a lot of sites offering legitimate and useful information out there are also some that seek to deceive or give flawed guidance and so for that reason I would stick to either advice from the Apple Support forum or other reputable/well known sites.
 
Alternatively, if yo are convinced that the issue is due to potential infection, and you have an active WSA subscription, then you can Open a Support Ticket, so that the Webroot Support Team can investigate/try to get to the bottom of the issue for you.
 
Please do let us know what transpires here and what ends up happening to resolve the issue...such information is useful to us in terms of helping other users who may come here with a similar problem.
 
Regards, Baldrick