This phrase (Do not hesitate, do it) represents me and I have it in all my social networks, but I don't know how to say it in Irish. Could you help me?

Literally, you might say:

Ná bí ag braiteoireacht, déan é!
Don't hesitate, do it!
[Literally, it's "Don't be hesitating, ..." but that type of structure is very common in Irish]

The second clause above sounds a bit abrupt to me in Irish, though, and this may be more natural, while also mirroring the "Be ..." pattern of the first clause:

Ná bí ag braiteoireacht, bí á dhéanamh!
[Literally: "Don't be hesitating, be doing it!"]

Wait for other comments, though.

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I'm not a native (or entirely fluent) speaker, so be sure to wait for confirmations/corrections, especially for tattoos.

Or the other way:
Déan é ach ná déan braiteoireacht. (lit.: Do it but don't do hesitation)