If they approached you and out of the blue and asked you (as the OP's question implies) if you wanted to engage in a sex act, would that not be entrapment?

Might. But he/she would probably be disappointed with what I've got to show. Done it on cam though.

Sure!

that sounds hot to me would love to in the right situation

I have jerked off for strangers who have asked me to in adult movie houses, adult bookstores, a hotel bar at closing time. I have met people briefly and joined them in their or my hotel room and jerked off for them. I have also done that at a secluded nude beach.

Absolutely, have a few times neighbors daughter in back asked me one time when caught me thru the window..God got so excited whn she watched came in seconds and did it agian for her to watch !!!

20something years ago I was at my gay neighbors backyard cookout/party. Long story short, up in the night I found my self drunk and sitting with an also drunk gay man by the fire pit. Our talk turned to sex. My cock started to get hard. He dared me to let him to watch me jerk off. I did. I liked it! Full disclosure: he finished me off with his mouth, the first male mouth on my cock. I have since advertised online for same and liked all. During that time, I discovered I like to jerkoff a cock (other than my own).

yes, done it in a porn cinema

I get asked quite often on the nude beaches I go to. I feel quite honoured when someone asks politely if they may watch.

Of course. It would be rude not to!!

Definately

Yeah - I like to set up a mutual masturbation session with one or two guys I don't know - They cum over and I am naked cock greased up and stroking edging my semi hard cock. They can watch or join in - I hope they join in.

Yes find it horny someone watching better if both do it together

Sure. Wouldn't be the first time. Kinda one of my kinks, actually. It started when I was youngster jerking with friends but over the years I've developed a taste for stranger fare.

So strangers never get a chance to ask. If I'm in a venue where a stranger would feel comfortable asking me that, My cock is already out, hard and getting stroked in front of everyone. BTW, I'm never the only one...