my 6 month old has started waking up way more through the night!

my 6 month old used to sleep from about 9:30-10pm-5-6am then would go back to sleep until about 9am after a bottle, but the past few nights he’s been waking up every 2-4 hours😅 we have another baby coming in April, so i’d really like to sleep train him to put himself to sleep if he wakes up and sleep through the night again.

-would this be sleep regression?

-if you sleep trained your baby, what method did you use?

*we don’t want to use the cry it out method*

-when did you move your baby to their own room? he’s not sitting up yet so he’s still in a bassinet, but he’s getting close so we’re about to move him to either a pack-n-play in our room or a crib in his room right next to ours. i’m scared to put him in his own room!