@ Electro
My daughters console/controller often did that on startup. We have even phoned Xbox Support, tried the usual , different controller, batteries, re-syncing, checked for updates ....
The way we solved it unless it was just a coincidence was from switching the console to Energy Saver Mode from Instant Start up. Since then it's been fine
Like I posted though. I had trouble when using Energizer AA Batteries but weird as it sounds they never sat as securely in the controller as normal AA throw always so I wondered when playing using the rechargables and it was a game that used the rumble feature
a lot , the batteries might just move a tiny bit and for a short time it would lose connection.
I've even seen people post they have used cello tape and stuck the batteries in more firmly, some have had success from doing that.
It's a common problem though, don't think I've got one friend online that hasn't mentioned having this issue at least once or twice. Chances are there's a number of causes, faulty console/controller, batteries not securely fitted, interference from other
devices
Pain in the backside when it does happen. Not so bad if your playing a single player game , not so good happening when I was playing something like Forza online lol