Then my friend, who is a much better runner than me, told me he likes to keep it simple. None of that stuff, just a Garmin watch for pacing/tracking reasons.
So I've started running "quietly" as well. It's great. Not only am I exercising my body, I'm cleaning my mind.
As a programmer, I've discovered that I almost always do better work, faster, if I've been taking my walks and exercise without audio entertainment. Don't know whether that happens for other people as well, but it's been pretty consistent for me.
(I do still wear cheap earbuds during exercise, though; you get far fewer interruptions when people assume you won't be able to hear them!)
A device will interfere between your inner self and your surroundings. Ideal when your surroundings are shitty. On the contrary, the lack of device will "force" you to search and find a nicer surroundings.
Introspection vs connection, choose your side.
I'd say novelty is important too. Whenever I do smth in new location or listen to new music, there's next to zero introspection. The usual location or known music seem helps introspection. In addition to that, if the location is unpleasant, it's hard to get into introspection mode.
TL;DR known-but-nice locations are best for introspection runs :)
[1] One did 240+ in 2017; the other 120+. Both broke the relevant records.
You brain knows how to fill the time. You may be afraid because you know what you brain will fill it with. But it may be worth to listen to what you brain has to say and try to get to terms with yourself :)
I think I know how you feel. I love long solo runs/rides/hikes. I'd lie if I said I was never afraid of random thoughts popping into my head.
I look at it as sort of meditation. There're plenty of articles regarding fear of meditation. Check them out. You're not alone afraid of being alone.
Let's not over diagnose this :)
Just sharing my experience. Unease usually doesn't come from nowhere. Everybody is different though.
Of course, no earbuds will block out the smell. (trains here dump their toilets onto the train tracks; it's officially not allowed to use toilets at stations, but it's not enforced).