My DD (4 months and 3 weeks, first child) has started throwing tantrums. To be clear, she's not crying because she's hungry/tired/in pain/hot/etc. they are proper tantrums and she's done two now. Both times she's been playing with something that we've moved away from her briefly (both were cool drinks she was about to tip over so we had moved them away to put a lid on them before moving them back into her reach) and she immediately started scream-crying and reaching for them. The first time it happened I was worried I'd pulled it away too hard and might have hurt her fingers but as soon as she got hold of the cup again she immediately relaxed and went back to her usual happy babbling that she does while playing. Same thing happened the second time, DH moved his cup to screw the lid on and as soon as he moved it back towards her the screaming stopped and she went back to giggling.
Not sure where this has come from as we don't rush to do her every want at all, when she's doing independent play and cries out of frustration (usually soft cries, very distinctly different from hurt/hungry/tired cries) we leave her to figure it out for herself, which she's very good at doing. She's usually such a happy baby, smiles all the time and at everyone she meets and loves to laugh so this new behaviour is quite a shock. She's also very independent usually, has been rolling, shuffling and sitting independently for a few weeks and started crawling backwards this week so it's not even like she's become dependent on us doing everything for her.
We're keen to try and nip this behaviour in the bud as quickly as we can if possible but all the advice for dealing with tantrums we can find is aimed towards older babies and toddlers that have the communication skills and capacity to reason (at least on a basic level) but she's not even 5 months yet so not able to understand those kinds of things.
Does anyone else have experience with dealing with tantrums very early or just have suggestions of things we could try? She's normally such a mild natured and sweet baby and we're keen to try and keep her that way and encourage her to grow into a well mannered child. Any help would be greatly appreciated, thank you