It's common for them to do that. Showing signs of readiness is normal but it is recommended to wait until 6 months. Under 4 months can be dangerous as baby's digestive system and gut flora is not developed to the point where he/she can handle solid food. Strictly Breast milk or formula is perfectly fine for at least 6 months. If baby is sitting up on his/her own and can pick things up to bring to his/her mouth that is usually when it is recommended to start trying solids.

I started my baby at 4 months .

Yep. DR said he was ready for solids but maybe a little taste of fruit first. I started giving my son banana at 3 1/2 months. Not all the time but little bites here and there