Can I leave flour to autolyse for long period of time?
Yes letting the sourdough sit at room temperature over night should work. This is in fact the way I handle the refreshing of my Lievito Madre usually and from my experience sourdoughs tend to be robust enough that some hours more or less should not matter much. When starting a culture it´s even common to let it sit at room temperature for up to two days between the feedings. But I would not recommend to let it sit for such a long time before storing it in the fridge again because even there the process does not stop entirely and also consumes some food.
To get more life into your dough also ensure it is sitting warm enough. For me room temperature at ~20°C works well usually but if you are experiencing trouble to get it started again aiming higher at around 28°C might also help as the bacterias are getting more active at warmer temperatures.
(Autolyse does not exactly mean refreshing/feeding of sourdough. It a process where just flour and water is mixed before other ingredients (yeast, salt, ...) are added to reduce kneading and improve taste and texture.)