@Crystal Lee,
There are tons of reasons why this could be happening, everything from alcohol or caffeine drinking at night (or too late in the afternoon), to undiagnosed sleep apnea, to stress, to loud noises that might not be enough to awaken you but are affecting sleep quality, to too much texting or computer usage at night that is getting you wound up.
If you think it might be physical, ask a doctor. In the meantime, try less caffeine during your day as it might be affecting you more, and longer, than you think (note: I am
NOT a doctor).