There is a massive misconception that littles must be actively doing something to be actively little. This is incorrect and not logical. It comes from the idea that littlespace is strictly a BDSM situation or kink--"bedroom only time" where you can do something to get "turned on". You aren't a lightswitch though and this isn't a situational thing. This is a personality base. You are always you, and if you are a little then you are always a little (note: a little is still not a child and has experienced growth, maturation, and adulthood so this does not mean a little = a child at all times
Littles are very much little all of the time or consistently in small ways throughout their everyday lives--even if it's only through their base thoughts and feelings. It doesn't mean they don't experience littlespace or have regressive thoughts, feelings, or even desires. It just means that they are naturally in a state where they "just are". Sometimes they express their little trait moreso than other times. It doesn't mean they switched "off" on being little though if they aren't expressing as much childish/childlike behaviors at some point.
You do not need to perform any action or inaction to be a little. You do not need to acquire or want to acquire objects to be a little. You do not need another person to magically "make" you be little. There is literally nothing you have to do or not do, and that generally means that there isn't necessarily a way to "force" you into "actively" being little at any given time.
Being a little is a personality trait. You cannot make someone be a little, and you cannot make someone not be a little. This means that for some people there is not a way to magically "activate" them and their special qualities.
A lot of littles will indulge further into feeling regressed with another person who is accepting of them and encouraging them to flesh out their feelings, but, even then, a partner of any sort should never be required to feel as yourself. You should not need to rely on someone else to determine your regression, and if it's a situation that only happens with a partner then you need to look deeper in yourself to determine if you are actually a little/regressor (maybe you are simply overlooking the times you were little/regressive without a partner's influence) or if you are just playing pretend sometimes via roleplay you just think is fun. The point there is that a little may roleplay as a child and feel it's fun and a form of self-expression but it doesn't make them any more or less of a little just because they manifest it through roleplay. And just because someone roleplays as a child for fun doesn't necessarily mean they are a little.
Many littles find that their environment can help encourage them to physically manifest their traits into obvious ways through actions or inactions. Sometimes this means setting up your room or safe-space as a nursery or playroom of sorts and acting out thoughts and feelings that come up for you--following them through and expressing them outwardly.
Sometimes it means just really relaxing and thinking all of your happy, regressive sort of thoughts and indulging in how you feel--acting how you feel without thought as to why. Some people find they can fall deeper into those thoughts and feelings by acknowledging them, embracing them, manifesting them, and spending more time thinking about them and scenarios related to those feelings. You may be able to flesh out your imagination and focus in on all of the tiny details on some little things you enjoy to get a feeling of that special "littlespace" manifestation. Plan out the details of an adult nursery, your trip to Build-a-Bear, or some make-believe special outing that only biological children seem to get to experience.
I would guess very much that you do experience regressive feelings more at certain times than other times but perhaps you have yet to really recognize or identify these times and what caused the feelings to manifest moreso than usual for you. Keeping a journal or log of times where you just "felt" like a kid would be helpful so that you could track when these feelings or thoughts happened and what directly may have occurred before you realized you were having these feelings/thoughts. Eventually, you could potentially play on that by recreating situations and scenarios that had caused you to react more childlike than at other times.
I could encourage you to read through our resources a bit further: