My baby is almost 8 weeks old and she won’t lift he head up during tummy time. She’ll just kick her legs and move her arms. But she’ll lift her head up when I’m holding her, either holding her on my shoulder to burp or if she’s laying on my chest, she will lift her head up and look at me. Is this normal? Do I need to worry since she’s doing it when laying on me? Could it be that she’s just not interested in holding her head up to look at anything?