Flirting

How to move communicating from social media to texting? Is there a way to just ask for his number?

There's a guy I'm attracted to and we are acquaintances who would see each other a few times a week as he'd drop orders off to my job. He gave me his Instagram one day because I mentioned a music interest and he said his friends were in a band and he'd give more info on them (which didn't happen)
Then shelter in place/quarantine happened and we instead caught up about downtime.
While I like him I had no way of gauging his interest except he was very nice to me and give me discounts like members discount with his employee discount or he would say no charge.

The problem is I thought we'd get to know each other off site but he rarely uses social media. He checks Instagram once a week so it's been more like having a penpal instead of a conversation. I thought maybe he is trying to keep professional boundaries but recently he DMer me that he doesn't use IG a lot because he takes bad pictures. I said they can't be that bad he looks fine and he said we have attractiveness in common then.

After he wrote that was the one time he came on IG again the next day instead of a week. Now it's more like twice a week but waiting for him to respond to 3 sentences for 3 days is so annoying and has no momentum.

Do you think he wants to be distant. Or I should just say hey, when you write back after a while I forget what I was talking about. Do you text more? Or will that be too aggressive and I should just keep dming and hope that opens us up more?
How to move communicating from social media to texting? Is there a way to just ask for his number?
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