Odd scar like lines appear/disappear on head

Twice in the past month I have had scar-like lines appear on head (I have a shaved head) and then disappear a few hours later. They look exactly like old scars (co-workers have commented about never noticing the scars before).  They are are not red at all and do not itch but are indented. It looks like I slept against something and it imprinted there but they both came on at random times of the day when I had not been sleeping.  As I mentioned they are not painful but I would love to know if anyone has any idea what they could be.  My doc doesn't know and I couldn't find anything like it on the internet.  

[Dr Santos]

Hi,
How are you? Are there other symptoms present? These could be due to calcification, soft tissue changes and conditions such as linear scleroderma that needs to be ruled out. Diagnostic tests such as blood tests and imaging studies (like x-ray or CT scan or MRI) may help determine the diagnosis. If it persists, it is best that you check with your doctor for proper evaluation. Take care and do keep us posted.