This problem could be caused by a number of things. Did you try to rest the NVRAM?
'''Step 1''': Press '''Command-Option-P-R''' quickcly when you turned on your macbook
'''Step 2:''' Release those key's if you hear the startup chime for the second time.
'''Step 3''': Does your macbook boot normally ?
To rule out if it is an software related issue, can you run Apple Hardware Test?
Depending on your version of Macbook:
'''Step 1:''' Press "'''D'''" quickly when you turned on your macbook.
'''Step 2:''' Run the tests
or
'''Step 1''': Press Option-D quickly when you turned on your macbook.
'''Step 2:''' Run the tests.
Last but not least, can you start verbose mode? Press '''Command-V '''quickly after startup