It's a normal facet of ADHD... Done it my whole life. Not constantly, but daily. The more I'm moving the more often it happens. Sometimes hundreds of flashes of "what ifs" a day. Sometimes only a few dozen. Part situational awareness, part heightened awareness, part intrusive thoughts, part catastrophizing, part imagination+reality. Depends on the situ. Sometimes emotions are attached. More often it's just me brain ticking through possibilities.
PTSD flavors it in certain ways via certain experiences. As a case in point I've been in probably a few hundred vehicle crashes of various types for work. I've also seen my fair share of other people's crashes. Some good outcomes. Some bad. So as I'm driving? That's what I see. All the different trajectories & possible outcomes. I happen to love driving, and that's partly because I can see so many outcomes at all times. I almost never feel trapped. Speeds, angles, everything comes together in a very fluid thing. It's relaxing. Unless I'm visualizing the cause and effects of spinning my wheel & standing on the breaks at 70mph (like a ballet pirouette, and then blood & dying... Or worse, all the breaking), or going off a cliff, into a pole, etc. That's when my suicidal ideation has kicked up, or my anxiety, or whatever.
Everyone, to the best of my knowledge, can do it. Most new parents do it for a short time, until they relax. Most experts in any field can look at a thing and see the possibilities present. ADHD people, and certain SPD people, do it all the time as a facet of incoming sensory information. PTSD people often do it in relation to trauma.