I may be able to bring you the reverse perspective, perhaps it'll be useful to you.

It's not rock solid theory, mind you, just some observations. I've recently had a shift in attitude. It's difficult to explain exactly, but I'm fairly sure I haven't been using Ti very much lately. It stems from not wanting to get caught in my usual Ti-Si loop. As a result, I feel ... different. I wouldn't go as far as saying "I'm an ENTJ for now!", I'm clearly not. But my usual functions (except Ne it seems) are totally discarded. I've been using a different kind of thinking, I can only suppose that's Te showing up.

There are plenty of positive sides. I get shit done so fast, I'd amaze myself if I cared. I also am less handicapped by my various fears and anxieties, I noticed. I seem to not visualized negative outcomes so much, and get less paralyzed by them fears as a result.
On the negative side, I am even less warm than I used to be (don't know where Fe went, but I don't miss it, it can stay the hell away).

All in all, I'm not sure what's happening to me recently, but there's clearly been a change. Is this the shadow mode? Could be.

You don't want the shadow mode though (it's supposed to be unhealthy), you just want to access Ti, perhaps?

If you read the INTP sub, you'll see a lot of very long posts/comments. I've always felt my "intp-ness" was most visible when I write and/or try to explain something.

So, you could try to write. You've said in your post it was hard to think and write about your experience. My take is that it's exactly why you should keep trying to do it. First simply describe, then try and analyze. And then draw conclusions. And do it again, draw different conclusions maybe, see your first description wasn't as correct as you thought, or that your analysis was lacking.

I'm recommending writing specifically because I had an ENTJ friend who absolutely sucked at what I just described. It made him feel very uncomfortable to even try (as it did you when you wrote your post). But it seems to me the easier way to access that shadow Ti.

Now that I think of it, my own experience from the beginning is irrelevant. Oh well, I'll leave it up anyway, it could serve in a way I didn't expect.

Hope you get better!