Step one for rebooting your career is NOT querying. I don't want to help you with this stuff; I want you to have already done it.
Step 1: Google yourself
Note the order in which your social media sites appear. I'll start with the first one I see when I google you. And I will google you.
What I want to see WHEN YOU QUERY is a robust following.
2000. Or more.
There are authentic ways to increase your followers, particularly on Twitter. Just do it. Don't complain to me that you don't want to. I get that enough from my clients who have to do this.
Rebooting your career is largely about telling me you have an audience who want your next book.
Step 2: Check Amazon for your previous titles.
I look for the number of reviews, and what percentage of the reviews are terrible. I look at the terrible reviews FIRST. If you have ten terrible reviews and all of them talk about price, I don't pay attention.
If you have ten terrible reviews and six of them mention they hated the plot, I pay some attention.
If you have ten terrible reviews and all of them talk about some aspect of the writing or the plot, I pay a lot of attention.
In other words, I try to pay attention only to reviews of your book written by real readers. Six people bitching about how they hated the plot tells me something else is at work (like it was a give away, or someone is targeting you) cause who the hell buys a book if they don't think the plot sounds interesting?
If you've had several books published and none of them have more than four or five reviews, the time to fix that is BEFORE YOU QUERY.
Step 3: Tell me about your mailing list.
Not how you are going to build one.
The number of people on it, and the open rate.
Step 4: Who will say nice things about the new book?
Your old blurbs aren't going to help us. We need new people who can be asked for new blurbs on the book.
Don't have those? That means you need to be more involved in the writing community. Rebooting a career will happen ONLY if you have other people willing to buzz about you.
I can help you reboot your career IF and only if an editor thinks there are people out there who will buy the book. Editors are going to do the same thing I am when I see your query: google you.
Thus, before you query:
1 Robust social media presence
2. Good and plentiful reviews of your previous work
3. Robust mailing list
4. List of people YOU KNOW will be potential blurb provider
Know too that I need to LOVE your books if I'm going to seriously consider doing a reboot with you. Rebooting is a lot of work that doesn't get compensated. That's not a deal-breaker, but if I don't love your books, it's drudgery. I'm not into drudgery as a rule.