Extreme dizziness when standing?

Okay, so when I go to sleep i have my phone plugged in on the dresser. Usually in the middle of the night, I'll wake up randomly and take it off the charger to bring closer so I don't have to get up as soon as my alarm goes off. Recently, maybe only the last month or so when I get up to take the phone, I get very dizzy, my heart starts pounding and I even feel a little hot. It only lasts for a minute or so, and I go back to sleep easily. Has anyone else had this happen? Not really sure what's causing it