The letter/notice you received from the IRS should have a identifying number that signifies the "type" of notice it is. The following website is useful in determining the reason you got the notice to begin with:
https://www.irs.gov/individuals/understanding-your-irs-notice-or-letter
That being said, I would contact the IRS at 800-829-1040 and get them to explain what it is they are working on and why. It may be relatively harmless. It doesn't sound like they are "preparing" your return...just looking at something in particular. It is important that you contact them as soon as possible about the matter so you can have some peace about the whole matter. Also, remember that the IRS will never contact you via phone, email, or text. When the IRS wants something from you, the send letters and/or notices.
