Rest service unavailable

Hi,

We have a problem with a REST service for our document portal.  (11.5)

In the morning when we want to login on our document portal we get a message service unavailable from our website builder .

When we log in a second time, there's no problem. Everything works.  The rest of the day, there's no problem.

It looks like appserver or tomcat is going to sleep mode over night .  When we check, we have 5 appserver processes that are available.

Are there any suggestions to prevent this from happening ?

Gerd