Randomize rows values in MySQL based on current data

I have a MySQL table wallet with real data and I want to randomize this data to similar values based on original.

For example, update amount column value on wallet table with a RAND percent (from -20% to +20%) for all rows.

With PHP will be:

foreach (Wallet:select('id', 'amount')->get() as $row) {
    $row->amount = $row->amount + ($row->amount * (rand(-20, 20) / 100));
    $row->save();
}

Thanks!