As near as I could tell, not very many. There were few really. Alexander came to the throne in 1801 by an uprising. His father Paul I was almost insane: he was cruel and dictatorial and when the nobility became disastisfied, they successfully revolted against him.
Alexander was on the throne the next day in 1801. That was not a revolt that he had to deal with, but it did change his life. He came to the throne. The Romanovs were a strange breed of monarch. Some, like Catherine (who married into the Romanov family, were absolutely brilliant and forward looking. Others, like Paul I, were terrible rulers.
Alexander avoided unrisings primarily by turning his attention to external affairs like his affiliation with Napoleon and economic trade with Great Britain. There was some attention paid to internal affairs, but not much. Not much was ever done internally, because Alexander refused to deal with the problem that Russia needed most solved and that was the enslavement of the serfs. It is not that he did not want to end the serf problem: it was that the nobility would have revolted if he did. That was enough to warn him not to go further. There was no revolt because he caved in.
Liberalism marked his thinking in the first decade of his reign and religious piety the second. He left most of the internal affairs to other more capable men.
During his religious decade he faced one revolt -- googled as the Semyonovsky Regiment revolt which greatly dismayed him. There were plots but they did not come to much.
The one remarkable fact about this Russian monarch: he at one point was the leader of the most powerful nation of Europe. He dealt with most things by conciliation, guile, charm and an ability to switch gears when there was opposition. Compared to Catherine, he may have been a mediocre ruler, but not many could be compared to Catherine.
