Why am I (47yo) having heart palpitations/flutters with sex?

[Jkthill]

Me and my wife’s sex life had been really bad for the last two years and we are trying to build it back up.  Here’s the problem.   I am a 47yo Male of slightly overweight (but losing weight) who is active and just had a physical with all good.  We will begin with foreplay and when I go to penetrate her my heart begins to flutter like crazy, I get really sweaty and lose my erection immediately.  She will try and get the erection back but it won’t come back.  What is wrong with me??  I have read up on sexual performance anxiety and am not sure if is that or something physical going on in my body.  I can masturbate with no issues also.  Only happens as soon as she touches my penis in any way.  As soon as she does my body goes crazy.  This is a recent issue and I have never had issues with sex.  Please help!  All advice is appreciated!