When the Author server restarts, it can look, to the users, like it is hanging because as soon as they click on a node in the left hand nav tree they see "Loading" in the central pane. It just sits there saying "Loading" for a long, long, long time.
This can be caused by having lots of old Workflow instances hanging around (check /etc/workflow/instances). In which case, you should ensure that you install the Workflow purge tool from Adobe. 
The purge tool by default will clear out any Workflow instances which are less than 14 days old (well the version I have says > 1 day but the code was actually > 14 days). It can be configured to only purge COMPELTED workflow, or ALL of them. However, beware that the default configuration (in my version 1.6.1 anyway) will only purge the following workflow models :-
Therefore, make sure to add in your additional workflow models.
I used an Xpath query, like the one below to get the counts of instances for each particular workflow model :-
/jcr:root/etc/workflow/instances//element(*, cq:Workflow)[@modelId='/etc/workflow/models/activate_entity'] order by @startTime
The list of Workflow models are available in /etc/workflow/models
This is now scripted up, so that I can get a count of all of the instances for each workflow model. You can improve the query above to add a date range to your query.
NB, older versions of this tool accessed a file directly on the filesystem - this stopped it from working on our hosted servers because of the repository location & needed to be modified.
The tool works really well, and I am sure that the newer versions of the tool (v1.6.5 at time of writing) are even better. Well worth installing.