Well, I have lost track of time myself and I found it very "disturbing". It could be that in therapy you are touching on something that is triggering you and you don't realize it yet.
Or something that is going on in your life that is triggering you, even an interaction with someone that triggered you to an unpleasant memory where you disassociated from it because it was a bad interaction.

Just keep track of these periods, write them down and for how long too. Also think about what you did that day etc, that could have triggered it to happen. Or even what you were thinking about too.

OE