In general, as long as you adhere to the rules of the Financial Industry Regulation Authority (FIRNA), you can buy and sell stocks as frequently as you like.
As a retail investor, you can't buy and sell the same stock more than four times within a five-business-day period. Anyone who exceeds this violates the pattern day trader rule, which is reserved for individuals who are classified by their brokers are day traders and can be restricted from conducting any trades.