I suspect that someone is trying to file a non-filers tax return for stimulus money...but...they've messed up in entering their own email address (or phone number for texting), and that screw-up just happens to match your email address (or phone number for texting).. They keep trying because they can't figure out why they are not getting the code sent to their own email/phone....it will never show up for them until they start over or fix their email address/phone.
That's just a guess on my part, but a similar thing happens many times each year. But, no way for TTX to trace it. IF you are uncomfortable with this, and just to make double sure you are OK, you might go into your account, and change your UserID and password for your account....write the new ones down in your tax file folder...because you will forget that you changed them by next tax season !! While you are at it check the phone number you've entered for your account too.