If we think earth is rotating along its axis and revolving around sun also. So earth cannot be an inertial frame. Similarly, sun is revolving around our galaxy, galaxy also moving in universe, Thus, Sun is also not an inertial frame.

Actually we cannot name a single thing in universe to have absolute rest or absolute motion state. So this concept does not actually exist but for practical applicability we can think earth to be inertial frame and solve problems.