もしかしたら and its alternatives are usually treated as stand alone 副詞（ふくし） (adverbs) in Japanese that are used to present hypothetical situations, and what could happen within those situations. These expressions are a combination of the adverb 若（も）し, the 格助詞（かくじょし） (case marking particle) か, and one of several combinations of する (したら, して, or すると). It is often translated as ‘perhaps’, ‘maybe’, or ‘possibly’.
As with many other Japanese adverbs, it will often appear at the beginning of sentences. Due to もしかしたら presenting hypothetical situations, かもしれない will regularly appear in the same sentence (although it is not required).

• もしかしたら、行（い）けるかもしれない。
  Maybe, I will be able to go.
• もしかして仕事（しごと）があるかもしれないから、今（いま）ははっきりしたことが言（い）えない。
  I may have to work, so I can't say anything for certain.
• もしかすると、アンちゃんも来（く）るかもしれないけど皆（みんな）は大丈夫（だいじょうぶ）？
  Maybe Ann-chan might come, but are you all okay with that?

As もしかしたら is a combination of もし ‘if’, か (presents a question), and したら ‘so happens that’, the literal translation is close to ‘does it so happen that’, or ‘should it so happen that’, with past or present tense being controlled more so by the following statement.

• もしかしたら明日（あした）も休（やす）むかもしれない。
  Perhaps I will take a day off tomorrow.
• もしかしたら昨日（きのう）だったかもしれない。
  Perhaps it could have been yesterday.