Multitrack Randomly Muting Tracks 15 Second after Hitting Play

If the mute is happening every time at the same point expand your tracks and at the Show Envelopes choice mute, keyframes dipping will indicate where the mute is happening during playback

If you've used a lot of effects - or come to that, just a lot of tracks, then the chances are that you've exceeded your hard drive's ability to stream them all at once. If it's an effects issue, then the gloriously simple answer is to use the little lightning bolt at the top of the FX section of a track to pre-render it. That cuts down the computer's work rate considerably - and if you need to you can always undo it if you need to make changes. I'd try that first before considering anything more drastic...