Is it 6 months both ways?
For most white collar roles, 1 month is the norm. As you get more senior, it would be 3 months.
For 6 months, I would expect it to be a C suite role.
Is it something you can negotiate down?
At least make sure it is paid notice.
Also, someone mentioned non-compete clauses. They are rarely enforceable and have been struck out by the courts on many occasions (a recent example is the Ryanair v Peter Bellew case)