Low battery warning when Mac is fully charged

Hi there,

My MacBook Air keeps displaying the message "Low Battery: Your Mac will sleep soon unless plugged into a power outlet", and the battery display suddenly goes to 0%, even if it showed 50%-90% of battery the second before. It eventually goes back to the original amount without me plugging anything in. Should I be worried about this or is it just a glitch? I've had this MacBook for less than a year; I don't expect the battery to have problems yet. Thank you in advance.