Trying to get back in

If your past experience is still verifiable and the reports would be favorable (not bad) and you still have your CDL, some of the larger carriers will bring you in and evaluate your skills and determine if they're comfortable advancing you to "experienced driver status" or want you to go through a trainer process to further evaluate. TMC, Roehl, Schneider, and others I think still do this.

I temporarily retired and stayed away 18 months (12 months longer than planned) and just recently decided I needed to get back to work. Applied to 6 major to mid-size carriers, and only one said I did not have satisfactory level of recent experience (Tyson Foods). But 4 years puts you into a different category, I suspect. Good luck.