if statement to activate a function after a time period (solidity)

Question

I want the following function to activate after 6 mins(360 secs) of contract deployment because my task requires a withdrawal lock. should I put if (block.timestamp > 360) before the function or inside the function just before the remaining code?

 function withdraw(uint256 amount) external updateReward(msg.sender) nonReentrant {
        if (block.timestamp > 360) {
        s_totalSupply -= amount;
        s_balances[msg.sender] -= amount;
        emit WithdrewStake(msg.sender, amount);
        // transfer: send tokens from contract back to msg.sender.
        bool success = s_stakingToken.transfer(msg.sender, amount);
        if (!success) {
            revert TransferFailed(); // revert resets everything done in a failed transaction.
        }}
    }

But I'm not even sure if if (block.timestamp > 360) is the right code for this case.