Op,
58 here, and I previously had an occasional FWB. and I'm looking for another - PM me! 
At your age, you should have no problem.
You can easily find a FWB or FB on ANY dating site. Just put "looking for FWB" or similar on your profile, and you will be inundated / spoilt for choice - particularly if you are bi, or bi curious..
You could use an adult site like AFF (but I think you may have to pay? It might be free for women - not sex discrimination at all…), or Fabswingers (My recommendation. Not just for swingers - LOTS of single guys / couples / women looking for casual sex. You would be classed as a "unicorn", and would be VERY much in demand!), but I really don't think you will have to.
Les inhibited? Probably. I certainly explored a more kinky side of sex with my FWB, and would like that to continue (damn lockdown!)
Feel free to ask anything. If I can help, I will.
Whatever you decide, know your limits, stick to them, and don't be pressurised into anything that you aren't happy with. Most of all, have fun! You only live once!