The Netherlands is an example that immediately came to mind, but Napoleon and the aftermath had a lot to do with that. Is your question limited to examples not done by external forces?

For that matter, does Rome count? Obviously, the nature of the rule for Augustus and his successors was extremely complicated and politically nuanced and didn't always involve direct hereditary succession (even when there weren't coups), but it could also be fairly described as a monarchy of sorts.

Spain became a Republic in 1873 to become a Monarchy again in Dec 1874, it would become a Republic once again in 1931 until 1939 when would become a Dictatorship to become a Monarchy again in 1975 until today.

There are multiple examples of toppled monarchies being restored.

In the 17th century, Oliver Cromwell chopped off King Charles' head and established the Commonwealth of England with himself as Lord Protector. After his death, his successor proved a weak leader, and former Commonwealth Men saw opportunities in restoring the monarchy, leading to the English Restoration.

The French Revolution established the French Republic, which gave way to the French Empire with Napoleon as Emperor. The Bourbon Restoration then restored the previous royal house to the throne.

The February Revolution of 1848 overthrew the July Monarchy and established another French Republic, which gave way to another French Empire, this time under the rule of Napoleon III.

The First Spanish Republic was overthrown in a coup that restored the monarchy.

The Second Spanish Republic fell in a (quite famous) civil war that nominally restored the monarchy, but that really installed Francisco Franco as dictator.

The Second Federal Republic of Mexico was succeeded by the Second Mexican Empire.

The Democratic Kampuchea regime (the era of the Khmer Rouge in Cambodia) was overthrown after invasion by Vietnam, leading to the People's Republic of Kampuchea/State of Cambodia, which lasted for over a decade before the Cambodian monarchy was restored.