Hi Folks,
Just an update since my original post.
For the past 10 months, I have been deactivating the Eco-mode when I start driving so my GLA250 no longer shifted to neutral at red lights. Then recently, the check engine light came on and I was told that my main and auxiliary batteries needed replacement. After replacing both batteries by myself (dealer wanted $900+), the problem seemed to have fixed itself. I'm not sure if this will work with others', but just wanted to share my experience.
*** Tip: Make sure to plug in an auxiliary battery backup before changing the main battery under the hood (in case auxiliary battery is dead as well).
Good luck!