2005 ford escape trans

sometimes my transmission has a little trouble getting into 3rd or 4th, no trouble on the rest of the gears, and the fluid still looks red! 6 cyl. automatic 120K. Any ideas?

Please explain “a little trouble”. Exactly what does it do?

Well it hesitates or lags when its time to shift like it’s having trouble. Just for a second or two but it’s noticeable.