Word tries to be helpful by automatically applying formatting to your document based on what you type. One example of this is when Word automatically creates a numbered or bulleted list for you when you enter some text that Word thinks should be a numbered or bulleted list.
When you type a number followed by a period and then press the Space Bar or the Tab key, Word automatically formats the paragraph as a numbered list. When you type an asterisk (*) and then press the Space Bar or the Tab key, Word automatically replaces the asterisk with a bullet and formats the paragraph as a bulleted list. You can cancel automatic formatting for the current paragraph by immediately pressing “Ctrl + Z” right after the automatic formatting is applied.
However, if you would rather not have Word apply automatic numbered or bulleted lists at all, you can turn this feature off. When you have a document open in Word, click the “File” tab.
In the list of items on the left, click “Options.”
On the “Word Options” dialog box, click “Proofing” in the list of items on the left.
In the “AutoCorrect options” section, click the “AutoCorrect Options” button.
On the “AutoCorrect” dialog box, click the “AutoFormat As You Type” tab.
In the “Apply as you type” section, uncheck the “Automatic numbered lists” check box or “Automatic bulleted lists”, or both. Click “OK” to accept your change and close the dialog box.
You are returned to the “Word Options” dialog box. Click “OK” to close the dialog box.
You can also learn how to use Smart Tags in Word to resume numbered lists. The article talks about Word 2007, but the feature still works the same way in Word 2013.