iPhone 6 16gb iMessages has constant white screen hangups

I have an iPhone 6 16gb on T-Mobile that is experiencing constant white screen hangups. When I go to open imessages, it will freeze up on a plain white screen for a good 5-10 seconds before letting me into the screen to see conversations with contacts. Sometimes after getting in after the white screen, it will open up a new message where you select a contact as if you were creating a new message. After exiting this screen, it will display no conversations even if there had been previous conversations. It then takes about 10 seconds or so for the message conversations to load up. I've experienced this not only in iMessages, but other apps as well. General slow loading, messages taking forever to send, messages stacking up to where it says Sending 1 of 5, and when all of the messages finally go through they all get sent at the same time. As mentioned, other apps such as Safari are slow to open and load. Texting and manually entering phone numbers will show nothing as I'm texting then all of the sudden all of the characters show up as if it's freezing. It's almost as if the whole system is lagging for 5-10 seconds before it catches up to itself. I'm not sure if this could be a T-Mobile thing or something to do with the phone. I have an iPhone 6s Plus as well on AT&T and have not experienced any of this at all. Both phones have the most recent version of iOS. I have reset the phone multiple times and just completed a full erase of the phone with a backup and am still experiencing the issues. Any thoughts? Should I just take it to the Apple store to see if it might warrant a replacement? It is still under warranty.