There's Difference between 合适 and 适合, which explains how 合适 is an adjective:
不合适的性行为有什么害处 (source)
Unsuitable sexual behavior has what harm找个合适的结婚对象,真的好难 (source)
searching [for] a suitable marriage partner [is] really difficult
whereas 适合 is an verb:
那种牧草最适合牛吃 (source)
That kind of pasture most suits cows to eat我适合什么职业? (source)
I suit what occupation?
However, YouDao lists 适合 as both a transitive and intransitive verb (i.e., no object):
vi. fit
I'm not sure this is correct as I don't recall ever seeing it as an intransitive verb, so want to check.
Question: Can 适合 be used as an intransitive verb?
If so, please give some illustrative examples.