Been playing some old tapes tonight, I've noticed on most of the tapes they sound good when I first hit play but after a few seconds the sound gets muffled, if I pause it and un pause it the sound will be normal again than after a few seconds it get muffled again. Is this most likely due to the tapes being old or could it be a head problem?

I think it's just the old tapes, just made a few sample recordings with a brand new sealed tape and it sounds fine, answered my own question.