Disconnection

Perhaps the issue is with the gaming server(s)? Do they have a script that restarts their servers nightly to clear cache and alike? Are the servers overloaded during late night hours? I do not know of any evidence that T-Mobile restarts their tower software. You should watch your gateway to see if it restarts itself. If you stream YouTube at 11:30 - 12:30 does the video stop? 

It sounds like you are experiencing an uncontrollable issue. 

It isn't the game servers because myself and my girlfriend both Have the same issue but she's not playing games while I am

The short disconnect may be caused by switching from one data channel to another. T-Mobile uses two main 5G data channels: N41 and N71.  The gateways generally perfer N41 if the signal quality allows. N71 is usually used when N41 signal is too weak or too noisy.   Late in the night, human activities start to ease off.  N41 may suddenly become a better option for the data connection. The gateway will switch you from N71 or a LTE channel to N41.  When this happens, your game server will drop you since your IP address may also change with the switch over.  

If this is indeed the case, your solution is to find a different spot that will allows you to lock on N41 all the time, or get an external antenna that offers better reception.