Hi Tushar, you can go to OSGI configuration, http://localhost:4502/system/console/configMgr and search for Apache jackrabbit oak TokenConfiguration. The Token expiration should have default value as 43200000 milliseconds, i.e. 12 hours (This suggests that AEM logout after inactivity of 12 hours). Check in you case if anything has been modified in this field.
Are you seeing this on fresh instance Or is this happening after some custom deployment?
Do you see error in error.log? Which AEM version are you on? Also, are you having multiple AEM instance open in same browser (not sure if this is Bug, but something happend with me 1.5 years back | it is like connecting to AEM with several users in the same browser tabs: the switch between the different tabs cannot work because i assume they all share the same session, aka the authentication cookie.)?
Can you try restarting your dev instance, as per my experience before, if we do any changes to Apache jackrabbit oak TokenConfiguration it will show authentication failed message.
After restart it should work properly,and the value you have edited 43200000 should be saved. Also check your error logs if you see any other error. If the issue still persists, please do check the error logs, what kind of error it is throwing. And one more thing what was the value of the Token expiration before you have edited it?