I think it's pretty normal to dissociate while driving - even those without PTSD do this, although to a lesser extent. I guess I'm lucky in that work is totally separate for me - most of the time, no matter how dissociated / severe my symptoms, if I have to go to work, they disappear while I'm at work. I can be feeling suicide, huge anxiety and struggle to get out of bed / leave the house - but if I'm called to work, I somehow instantly switch into work mode. Like playing a role I suppose. My problems (for the main) go away. Within minutes of leaving work, they come back again.
I understand your fear - being the breadwinner and worrying if it happened at work and you can no longer work, it could be disaster for your family in terms of financial stability. HOWEVER - think of it this way - the dissociation is 'merely' a symptom of anxiety (albeit pretty bad!). And clearly, it will intensify the more anxious you are - you are triggered somehow, feel highly anxious, dissociate, then worry further about the implications of this - which will leave you MORE anxious, and dissociation will probably worsen.
When I have fear around the level of dissociation I have, I've found it helpful to remind myself of this 'it's ok, November, yes, you are feeling dissociated, and that's ok - it purely means you are highly anxious right now, but you're not in danger. Your mind is doing this to PROTECT you - you can trust it, it will be ok". Another thing I find very helpful is to remind myself 'this is a symptom of my anxiety - it is harmless and I am not going crazy'. That helps me reduce the bulk of the anxiety and helps me feel less dissociated - or at the very least, prevents it becoming more severe.
I'd encourage you to talk to your Dr, you may need some additional meds for anxiety; and talk to hr T also, work out if there is anything at work that is triggering the anxiety - is it extra stress, responsibility, time pressure, or a co-worker or boss that triggers you to dissociate? Identifying the triggers can help you feel more in control, because you can 'expect' them in advance and come up with ways to alleviate the higher levels of anxiety.
Hope that helps!