Disable apps that you don't need, that will help. Also if you started facing this issue recently then check which app you installed as that might be causing an issue.
I am unrooted as well and my Mega is running fine with no lags, if you have updated with the Galaxy Gear update recently then go back to the previous version as some people have complained of lags and heating after the update, which I have not infact I feel its a bit more responsive after the update.
Sent from my GT-I9152 using Tapatalk