If I received a 1099k for temporary work, is it considered self employment?

Possibly.  If you were not an employee of the company you were working for, then yes, you would be considered self-employed and subject to self-employment taxes. 

The three main determining factors to decide if you were an employee or self-employed are 

1. Did the person paying you have behavioral control as in, did they control how, when and where you did your job?
2. Did they have Financial Control?  Did they provide you with the tools, vehicles, etc. to do the job?
3. What was the agreement?  Did you believe you were an employee or self-employed?

If you meet the criteria for self-employed, then you would enter your 1099-K in the business income section of TurboTax.  You can also deduct your expenses incurred to do this job, including mileage and tools purchased for the job. 

If you were an employee and misclassified as self-employed, you would need to file form SS-8 with the IRS by mail.  You would still need to include the income you received from the job on your tax return.