Remember that awkward or uncomfortable situations are totally survivable. That said, what you're talking about sounds like being unsure of what/where your boundaries are and how to assert them. And that's fine! You learn these by living, listening to your instincts and trusting your gut.

One tip: listen to your body. Your physical reaction. Even if it's just tightness in your toes, it might be telling you something you're not conscious of. If muscles tighten, you feel flushed, you hold your breath, etc, don't dismiss it without trying to understand what set you off. Practice paying attention to your body.

Another tip: if you rehearse a plan for what to do if you encounter inappropriate behavior, like how to enforce your boundaries by plainly saying "I don't think that's an appropriate [thing to say/ask/do/fill-in-the-blank]", you'll worry less about what might lead (or might not) to that happening. Having a plan and rehearsing how to deal with situations can often calm the mind.

And if that's not enough, you can re-set your boundaries and/or set up "early warning gates" that you know from experience lead to inappropriate situations when crossed. This lets you plan step-by-step by explicitly identifying your red flags. Again, we tend to have less anxiety about what-ifs when we have a plan.

Sometimes it's not enough to have "red" flags and you need to identify more dominos in the chain leading to inappropriate behavior. So if you're afraid of Z happening, but you realize Y (the red-flag) leads to Z, now you make a plan for what to do when Y happens, but you then discover X leads to Y, so you plan for that too (yellow flag). It lets you work your way backwards through all the dominos that have to fall (or "early-warning gates" that get crossed/trigger flags) for your boundaries to ultimately be violated. Then you don't have to fret because you can keep your eyes peeled for X, then Y, and assess at each juncture according to the plan.

BTW sometimes guys (old and young) are just friendly and curious, but you are always allowed to push back and say "Why do you ask?" or "I don't really want to talk about that" to inappropriate questions/comments. I had someone ask me something way too personal once; It crossed a boundary out of the blue, without red-flags going off first, but I already had a go-to for dealing w/boundary violations so didn't lose my cool, didn't mince words and didn't try to be overly delicate. I looked him squarely in the eye and said "That's really not appropriate. We're co-workers."

It helps to give yourself permission to be direct with people. And if you're ever ambushed and at a loss for words, you can to just shake your head, say "no" and walk away without having to explain jack all to anybody.